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Buggerrats
07-31-2006, 04:20 PM
Any problems reloading once-fired brass? I purchased 500 pieces and each one has the shoulder blown forwards 0.050". Normal resizing die will not correct the shoulder. Were some FN 5.7x28mm weapons maufactured with incorrect head space? Did this guy shoot these rounds in some oddball caliber for which he had previously not been able to get ammo? In 50 years of reloading I have never seen bras do this. Any thoughts?

btown02
07-31-2006, 04:21 PM
Welcome to the forum. I'll move this to the reloading section for you.

colorado5.7
07-31-2006, 07:15 PM
I have the same problem with some of my brass, and would like a solution also?

revolver shooter
07-31-2006, 07:53 PM
I was having the same problem, to the point that after a couple of reloads I would get many FTF in both my PS90 and IOM. I do not know why it happens, maybe it has something to do with the bottle neck case in a blowback actiion.

What I figure out was that my loading dies were not resizing the case fully. First I made sure that the reloading die made very good contact with the shell holder. This helped, but did not cure the problem. I considered sending the dies back to tne RCBS, but decided to test my theory with the shell holder instead.

I annealed the shell holder and then chucked it into my lathe and took .020" off the top of it, then heateated it again. This let me adjust the die enough to get it so that it sized the case to within .002" of a factory round.

The feading problems have gone away, but the case life is rather short. I only get six or seven reloads in a lot of cases. They crack at the neck. Probably working the neck too much.

I am open to any other suggestions

mtopero
08-02-2006, 02:03 AM
I too was a bit surprized at the brass response when fired. :rolleyes: Rounds fired in the handgun moved the shoulder out considerably. I did a rough check of the distance to the shoulder in the chamber, and compared it to a new round. Chamber about 50 mils longer. So why not a headspace problem? With barrel out of the pistol I put a round in the chamber and noticed two things - the shoulder of the round doesn't reach that of the chamber by about 50 mils, and it is quite loose along the body of the round.

It appears to me the round is designed to headspace on the mouth of the case, like other handgun rounds like 45 auto, 9mm, 40 S&W etc. If that is the case, best not be crimping the bullets on 5.7x28 rounds much. And be diligent with case trimming to original length.

Also, if that is indeed the case, we should have good reliability (plenty loose fit in the chamber) but poor brass life. Only recourse I can think of is to have RCBS or others make sizing dies that resize the as fired case properly to fit the chamber.

I did notice the PS90 chamber to be tighter along the side of the round, but it has the same relatively long distance from chambered round shoulder to chamber shoulder.

By the way, I use Redding dies, and they have worked well for me in this cal.

Sorry for so many words. Couldn't get these thoughts in a nut shell......

Rnelson11
08-02-2006, 05:33 AM
The shoulder moving forward 0.050" is not very much. The hotter the load the more the shoulder will move, especially using 55 grain bullets. I have an original set of RCBS dies, bought when they were considered special order, and I have never had a problem with re-sizing.

The shoulder is the life of the case. Moving the shoulder back during re-sizing will eventually cause cracks at the shoulder and if you don't catch them during inspection they will split when fired. I've had several split when fired but it's never caused a problem other than a bad chrony reading.

Another problem with the 5.7x28 is the primer pocket. If you load 'hot' the primer pocket will stretch causing the primer to become loose. This will cause ejection problems. It's best not to remove the military crimp. Inserting a new primer is a little more difficult but it keeps the pocket tighter for a longer time. I measure the primer pockets before reloading and if they are more than 0.174" I don't reload them.

mtopero
08-03-2006, 01:18 AM
In the normal headspace on the shoulder world (like 30'06) .050" is more than a lot, I think it's dangerous. With the 5.7x28 apparently headspacing on the case mouth it becomes just a brass life issue. I have seen shoulders move out noticeably in belted magnum cases that headspace on the belt. In some bolt guns one can take advantage of that to neck size and get a little more powder capacity.

BSlacker
08-03-2006, 10:40 AM
This much shoulder movement is normal in a blowback system. There is no headspace at the time of ignition in this system. The round is pressed into the barrel at the datum line on the shoulder by the bolt face such that there is no space left, it is held in place by the recoil spring. There is no true lock up in this system so that when the round is fired the case expands and delays movement of the slide, this is where I think the coating comes in to play it adds friction, once pressure decreases the case will shrink and can move rearward this is when the shoulder is moved forward as the case starts to move the slide while pressures are still high. My measurements of once fired brass shows only about .003" variance on shoulder movement.
What we think of as unacceptable shoulder movement, .050", in bolt rifles and locked breech handguns, is only a problem in two areas.
This much movement means some reloaders will not get the shoulder back far enough to close the gap between the slide face and barrel it is normally about .008" with factory brass. My experiments showed that about .012" positive case shoulder length the gun won't fire due to being out of battery. This should be good enough to keep the case web in a safe area and should produce no firing pin movement with cases that have excess shoulder length.
Another is case life it will be shorter than expected from "normal" handgun brass.
For these reasons I think it is safe to reload a couple of times and pitch them.
Reloading for 5.7 is not the same as locked breech systems so be careful about removing the coating and brass life. :)

Buggerrats
08-03-2006, 01:28 PM
This much shoulder movement is normal in a blowback system. There is no headspace at the time of ignition in this system. The round is pressed into the barrel at the datum line on the shoulder by the bolt face such that there is no space left, it is held in place by the recoil spring. There is no true lock up in this system so that when the round is fired the case expands and delays movement of the slide, this is where I think the coating comes in to play it adds friction, once pressure decreases the case will shrink and can move rearward this is when the shoulder is moved forward as the case starts to move the slide while pressures are still high. My measurements of once fired brass shows only about .003" variance on shoulder movement.
What we think of as unacceptable shoulder movement, .050", in bolt rifles and locked breech handguns, is only a problem in two areas.
This much movement means some reloaders will not get the shoulder back far enough to close the gap between the slide face and barrel it is normally about .008" with factory brass. My experiments showed that about .012" positive case shoulder length the gun won't fire due to being out of battery. This should be good enough to keep the case web in a safe area and should produce no firing pin movement with cases that have excess shoulder length.
Another is case life it will be shorter than expected from "normal" handgun brass.
For these reasons I think it is safe to reload a couple of times and pitch them.
Reloading for 5.7 is not the same as locked breech systems so be careful about removing the coating and brass life. :)
I am tempted to accept some of your response except than one responder reports excess headspace in his chamber. If so, this would mean that either FN is manufacturing guns with chambers out of spec or cartridges out of spec. I don't have my PS-90 yet so cannot experiment and if the above is true, I can't reload and don't want the gun although I could rechamber the rifle.

In the normal headspace on the shoulder world (like 30'06) .050" is more than a lot, I think it's dangerous. With the 5.7x28 apparently headspacing on the case mouth it becomes just a brass life issue. I have seen shoulders move out noticeably in belted magnum cases that headspace on the belt. In some bolt guns one can take advantage of that to neck size and get a little more powder capacity.
This talk of the round chambering on the mouth makes no sence at all. Having a shoulder, any case headspacing on the mouth is causing all sorts of problems especially the expansion I complained of. Is there actual evidence from FN that these rounds are supposed to headspace on case mouth?

The shoulder moving forward 0.050" is not very much. The hotter the load the more the shoulder will move, especially using 55 grain bullets. I have an original set of RCBS dies, bought when they were considered special order, and I have never had a problem with re-sizing.

The shoulder is the life of the case. Moving the shoulder back during re-sizing will eventually cause cracks at the shoulder and if you don't catch them during inspection they will split when fired. I've had several split when fired but it's never caused a problem other than a bad chrony reading.

Another problem with the 5.7x28 is the primer pocket. If you load 'hot' the primer pocket will stretch causing the primer to become loose. This will cause ejection problems. It's best not to remove the military crimp. Inserting a new primer is a little more difficult but it keeps the pocket tighter for a longer time. I measure the primer pockets before reloading and if they are more than 0.174" I don't reload them.
I just have to disagree, 50 thounsandths is very large. During my 50 plus years of reloading I have overloaded many cases and never seen the shoulder move forward. My .416 Rigby is no sloutch and shows no problem. My 218 Bee is really stuffed with powder and way too hot but the shoulder never has moved. (p.s. I am no proud of my overloading just saying I have done it).


I was having the same problem, to the point that after a couple of reloads I would get many FTF in both my PS90 and IOM. I do not know why it happens, maybe it has something to do with the bottle neck case in a blowback actiion.

What I figure out was that my loading dies were not resizing the case fully. First I made sure that the reloading die made very good contact with the shell holder. This helped, but did not cure the problem. I considered sending the dies back to tne RCBS, but decided to test my theory with the shell holder instead.

I annealed the shell holder and then chucked it into my lathe and took .020" off the top of it, then heateated it again. This let me adjust the die enough to get it so that it sized the case to within .002" of a factory round.

The feading problems have gone away, but the case life is rather short. I only get six or seven reloads in a lot of cases. They crack at the neck. Probably working the neck too much.

I am open to any other suggestions
At least two responders have mentioned this problem in relation to blow-back actions. I have used dozens of blowbacks without a problem however I did consider this and I think one would then also see some expansion of the rear of the case as it would be free of the chamber at the same time the neck was being pushed forward

BSlacker
08-03-2006, 02:55 PM
I repeat this is not a locked breech design. It has NO headspace in chamber. Normal headspace concerns don't apply here. The cartridge is pressed against the datum line of the shoulder area of the case/barrel and the bolt face/case bottom while in battery. It does not headspace on the shoulder or case mouth it rest on the shoulder and case bottom. If you want you can easily check this out.
If you remove the slide/barrel remove the barrel and insert an inert cartridge then reinsert the barrel making sure to snap over the extractor you will see that the cartridge is held in place by the recoil spring pressure and there is a .008" gap between slide and barrel end remove the case and you don't have this gap. The cartridge is held tight it has no space therefore no headspace. Just try it before you think you know how this works. This is not a normal locked design that has a given space this is variable space and adjust to the shoulder length. You can't trouble shoot it like it is something it is not.
Terms like headspace don't apply to this design there is no SPACE.
The shoulders movement numbers of .050" are correct and not a safety issue if loaded a couple of times. This alone should tell one that this design is different. If a rifle had .050" shoulder movement it would be very bad. The case would rattle in the chamber so why doesn't the 5.7 case even move or rattle in the chamber if it has excess headspace and is so loose? :)

darkgael
08-03-2006, 11:31 PM
I am concerned about this shoulder movement also. I have always operated with the understanding that "headspace" meant the distance from the bolt face to a datum line on the "shoulder" part of the chamber.
I do not, really I don't, mean to be argumentative but I do not understand the idea that "there is no space". I have a couple of blowback pistols - a .25 and a .32 - the cartridges "headspace" as straight cases do, on the mouth of the case. I do not, at this point, see why a bottleneck case should be any different in so far as having headspace, though spacing on the shoulder.
None of the factory rounds that I have fired have anywhere near the shpulder movement that my last set of reloads had (described in the 55gr. thread); movement was a full 1/16th of an inch.
If this is normal, then OK but all of my hackles rise when I see something like that come out of my gun.
Question: how about resizing the neck only (I know - it's an automatic) and not setting the shoulder back? I have a dummy round made like this and the pistol goes into battery.
Ideas??
Interesting issue.
Pete

mtopero
08-04-2006, 02:44 AM
Now it appears we have some interesting new insights. First, I don't think we are all thinking the same thing with the term headspace. Perhaps I should not have used that term. I agree there may be no "space" between the bolt face and the unfired cartridge in a blowback design. By its nature the bolt will go as far forward as it can, either stopped by the cartridge (which stops in the chamber on the shoulder or neck) or it stops on the action or barrel like it does when there is no cartridge in the chamber. If the cartridge case were too short, there would be "headspace" - the cartridge would be loose in the chamber because the bolt would have stopped on the action or barrel. I think BSlacker said he measured 8 mil gap, but I don't know how he knew the cartridge had stopped on the shoulder instead of the neck. All this assumes the bullet is not jammed into the rifling like some folks do to fire form cases.

What I tried to relate was that based on my measurements on a 5.7 pistol barrel (only, the gun was disassembled), with a factory cartridge, the cartridge was not stopped in the chamber by the shoulder. The shoulder was too far back to reach that area of the chamber. Soooo, my conclusion, based on the fact the cartridge was loose on the sides, it must be stopped by the neck (no marks on the bullet). That doesn't necessarily mean there is anything wrong, that's OK. We just don't want it loose.

darkgael made an interesting observation:

"Question: how about resizing the neck only (I know - it's an automatic) and not setting the shoulder back? I have a dummy round made like this and the pistol goes into battery."

This supports my premise if the case was fired in the same gun. The dummy round has a shoulder location that more closely fits the chamber, and the pistol swallows it. I contend it would not if what some are saying were true, namely that the shoulder moves out as the cartridge is being extracted. Then it wouldn't fit with just neck sizing.

I wonder if darkgeal's 55 grs load fired brass, if neck sized, would chamber. He said the shoulder moved out more.

Maybe collectively we'll figure this out.......

darkgael
08-04-2006, 08:08 AM
Yes, a case neck-sized will chamber and fire; how many times this can be done I do not know yet. I shot four of them yesterday. As far as the cases with the shoulder blown forward are concerned, I need to do more with that. Before reloading them, I tried a dummy, which went into battery. The loaded rounds, however, will not go into battery. I have to check more about this.
Pete

BSlacker
08-04-2006, 10:01 AM
In a normal fixed chamber, as in bolt action, the headspace is from bolt face to a point called the, datum line of the shoulder, this is in general. This is fixed space, once the bolt is closed headspace exist and is set, it is fixed. When the round fires the cartridge expands to fill this fixed space and the case will be stopped there are no further shoulder movements or expansion only shrinking back.
In this design there is no space. The cartridge is held between the bolt face and shoulder datum line by pressure of the recoil spring. The barrel and slide are not locked together they float and are in contact with each orther through the cartridge. There is a gap between the slide and barrel breech end they don't even touch much less lock. Comparing this to other blow back actions is not relevant it is not the same. You may have seen many small caliber blow back firearms but this is not one of them. The pressures here are much higher and it is a modern design. There are many forms of blow back this is just one that is not typical of past designs. All you have to do is a test like I have described. With careful examination, I did mine under a microscope, you can see that the cartridge is trapped there is not any movement of the round in the chamber there is no space to expand and fill. The expansion and shoulder movement is dynamic. It is not expanding to fill a empty space as in a normal bolt action there is no space. The shoulder is moving forward as the slide moves away from the barrel, while there is still pressure to move the shoulder. Lower pressure rounds give less shoulder movement. My medium reloads give about .035" movement. Faster factory loads give the .050" that most have found on once fired factory brass. This would not be the case if the headspace was fixed. It is why I call it dynamic it happens while the slide is in movement well after ignition during pressure decrease. This is why it is so important to get this right there is still considerable pressure in the chamber when the movement occurs.
There is no headspace at the time of ignition! If the chamber had .050" headspace to account for this shoulder movement as in a normal rifle then the cartridge would rattle in the chamber and split the case when fired. Have you noticed this? No, the cartridge is tight and good cases don't split everytime do they.
It is just confusing to compare this system to normal rifles and hangduns or even other delayed blow back systems and it in no way resembles a straight blow back fixed barrel as in many rimfires and small caliber centerfire blowback operated handguns.
I am just trying to help people understand this is a different system the fired cases can't be compared to normal systems. This makes reloading 5.7X28 different and not for the novice IMHO. If you don't have a good system to check shoulder length I don't recommend reloading this round. One could easily have case head seperation. Yes, I cut a case to see where the case web is in relation to chamber support. It doesn't have much leeway IMHO. Be careful!
The pic below are what I am using to measure shoulder length.

http://img.villagephotos.com/p/2006-1/1128723/DSC_0005.JPG


http://img.villagephotos.com/p/2006-1/1128723/DSC_0006.JPG

The Caliper based one is a Stoney Point unit with a custom insert for the 5.7 case. The Dial indicator unit, I made the adapter, uses the factory barrel and chamber to compare shoulder length to factory rounds. This way I have two systems that agree. I did not fire a reload until I had completly understood the system and the relation ship of the barrel and slide chamber size. This chamber adjust to accomodate different lengths of shoulder get it to long and case head seperation is possible IMHO. I don't want anyone to get hurt by applying wrong info to this issue. :)

BSlacker
08-04-2006, 10:33 AM
Mtopero, Coat the neck and shoulder area of a factory round with dykem then insert into the barrel/chamber and rotate. You will find marks on the shoulder where it rest, not the neck. It makes no sense to rest on the neck area this will not provide the seal needed to operate the system this system is a closed gas system providing the blow in the blow back. I say again do not fire reloads that you don't KNOW where the shoulder is. This can lead to disaster.

darkgael
08-04-2006, 11:01 AM
Thank you for the posts. Very helpful. I have a dial indicator and a good caliper. Where did you get the custom insert for the caliper? Did you make it?
Again, thanks.
Pete

BSlacker
08-04-2006, 11:34 AM
I made the insert although I think Stoney Point would make one if asked. I took the hole size from a factory case datum line then compared the hole size and adjusted a one thousand inch at a cut to get on this line. In order to get more info I will make two and send them to two who already have the SP system it would help if they had a chrono as well. Just email laserfxer@earthlink.net. First come first served.
I would like feed back on once fired and reloads from other handguns.

nvreloader
08-04-2006, 02:53 PM
If you have a Stoney Point Chamber-all Bullet compariator set you can use the the 28 cal (7mm insert, fired cases) and (25 insert, sized cases) to check the shoulder length of the factory case on the shoulder, on any fired case and then resize the case and see the differences.

On the sample of fired cases I have, fired from pistols and sub gun, the movement of the shoulder is anywhere from .035" to .55" on the fired cases.

Fired cases measures averages .965", (shoulder length), resized cases average .930"

Factory cases measures ???

The RCBS dies I have will setback the shoulder to the spec's of .930".

As I do not have any factory ammo yet, I do not have the shoulder lengths using the above methods, to see or have a standard to check by.

If any one would care to post this info, It would give everyone a starting place.

I just recieved my reamer for this case and in the process of chambering a bolt rifle for this case, and also have a 17 and 20 cal using the same case.

Another item to remember is that DIFFERENT POWDERS have DIFFERENT PRESSURE CURVES when burning.
This was one of the problems we had to LEARN when reloading the AMT 44/357 Auto mag in the early 70's, and the powders and bullet combo's available then.

When the round is fired the first thing to seal the chamber is the neck/shoulder area, (due to the internal pressure), the base of the case then moves rearward untill the case head hits the breech/bolt face. After the pressure drops to safe levels, normal functioning of the pistol occurs.

The pressure curve of the burning powder and bullet weights effects the cyclic action (impluse) and the overall shoulder lengths in this pistol, try differnt burning rates of powder/ bullets weights to see for yourself. Just measure before and after, what did you find?

nvreloader

BSlacker
08-04-2006, 06:02 PM
Nvreloader, thanks for the info. I am seeing the same .035" to .055" based on the load.
This large movement in fired brass shoulder length based on load is only possible in a nonlocked and zero headspace system. Upon firing the cartridge case doesn't move back to the breech/bolt face to fill a fixed space as in a bolt rifle because the bolt face of the 5.7 is always in contact with the cartridge in the 5.7 system before firing, there is no space to fill. In a fixed headspace system like a bolt rifle the case shoulder is moved the same give or take a couple of thousands each firing no matter the load as long as the load is within reason. Because headspace doesn't vary. Unlike this where it varies with load and is extreme. What would one think if their bolt gun fire formed case shoulder measurement varied .025" over a moderate load range.
If you accept that it is a zero headspace system nonlocking then a question should arise. What happens to shoulder length when a round is chambered during cycle? It shortens about .003 to .005 because the round is stopping the slide against the stationary barrel at the datum line of the cartridge. This is not an issue with a locked breech fixed headspace system. Once you can see this zero headspace unlocked thing alot of questions come up. :)

Buggerrats
08-06-2006, 01:40 PM
I repeat this is not a locked breech design. It has NO headspace in chamber. Normal headspace concerns don't apply here. The cartridge is pressed against the datum line of the shoulder area of the case/barrel and the bolt face/case bottom while in battery. It does not headspace on the shoulder or case mouth it rest on the shoulder and case bottom. If you want you can easily check this out.
If you remove the slide/barrel remove the barrel and insert an inert cartridge then reinsert the barrel making sure to snap over the extractor you will see that the cartridge is held in place by the recoil spring pressure and there is a .008" gap between slide and barrel end remove the case and you don't have this gap. The cartridge is held tight it has no space therefore no headspace. Just try it before you think you know how this works. This is not a normal locked design that has a given space this is variable space and adjust to the shoulder length. You can't trouble shoot it like it is something it is not.
Terms like headspace don't apply to this design there is no SPACE.
The shoulders movement numbers of .050" are correct and not a safety issue if loaded a couple of times. This alone should tell one that this design is different. If a rifle had .050" shoulder movement it would be very bad. The case would rattle in the chamber so why doesn't the 5.7 case even move or rattle in the chamber if it has excess headspace and is so loose? :)
I agree with most everything you say. When I spoke of headspace I was referring to zero headspace. Not having a werapon yet I can't judge the problems. However, if you are saying that a fired case that has the shoulder moved forward can bereloaded without moving the shoulder back, that is great! and I would like to know if that is true. What confounds me (and having fired and reloaded most every non-locked breech weapon ever manufactured) why would the original case be designed with a shoulder in the wrong place (so to speak). It would seem that the original case would be designed with the shoulder already forward and then we would not have a streched brass problem. THis is all based of course upon my assumption (from what you have said and I may still be misreading you) that as I said above, the case can be re-fired without moving the shoulder back. Thanks for you help.
Roger

BSlacker
08-06-2006, 04:53 PM
I am saying you must resize the case and it is best to get it close or you will have a possible problem with case head seperation. If the case were to be left unsized then the web is .035 to .050 passed where it is supported properly this is dangerous. There is a considerable amount of unsupported area of the web of a normal case. This is a non locked zero lengthwise headspace system the shoulder movement is dynamic it occurs as the slide and barrel begin to seperate after ignition. The case is not expanding lengthwise to fill a fixed headspace like in a conventional rifle or handgun. And there is a danger of getting to much web area unsupported.
Make your gun safe and look underneath the slide with barrel installed and with an inert case, properly sized, chambered in the barrel and the extractor snaped over the rim you will see what I am talking about. Just try to move the exposed case lengthwise it won't move it is trapped, no space. You also will notice the unsupported area. The breech end of the barrel is tapered such that it doesn't support the case totally as in a fixed system.
For people who don't resize please do this and see the unsupported area.
You can't think of this system like a normal one with a tiny amount of space around the cartridge in all directions before ignition. Lengthwise there is no space, it has space around the case outer shell. I don't think it will help a whole lot with accuracy to tighten up the chamber diameter because the cartridge is already held steady and consistant in the chamber.
This system of no lengthwise gap or space is so that at ignition there is a gas seal already it doesn't develop it just gets better for a period of the delay. The case can expand in circumference at ignition and press the coating onto the chamber wall. I think the coating is used to control slide barrel movement, sort of the lock delay in some way. Anyway this is a very subtle system unlike anything to date. I am not sure they had reloads in mind when it was designed. :)

darkgael
08-06-2006, 05:25 PM
"I am not sure they had reloads in mind when it was designed."

Yeah, I have sure gotten that impression.

Pete

mtopero
08-07-2006, 02:21 AM
Maybe they had NOT RELOADING in mind..........

Medula Oblongata
08-08-2006, 06:50 PM
FN has told me over the telephone that this caliber is NOT reloadable (this was 3 or so years ago before the civilian launch of the pistol). I reloaded it anyway, and have had great success after severely modifying the RCBS dies.

Buggerrats
08-14-2006, 04:43 PM
I am saying you must resize the case and it is best to get it close or you will have a possible problem with case head seperation. If the case were to be left unsized then the web is .035 to .050 passed where it is supported properly this is dangerous. There is a considerable amount of unsupported area of the web of a normal case. This is a non locked zero lengthwise headspace system the shoulder movement is dynamic it occurs as the slide and barrel begin to seperate after ignition. The case is not expanding lengthwise to fill a fixed headspace like in a conventional rifle or handgun. And there is a danger of getting to much web area unsupported.
Make your gun safe and look underneath the slide with barrel installed and with an inert case, properly sized, chambered in the barrel and the extractor snaped over the rim you will see what I am talking about. Just try to move the exposed case lengthwise it won't move it is trapped, no space. You also will notice the unsupported area. The breech end of the barrel is tapered such that it doesn't support the case totally as in a fixed system.
For people who don't resize please do this and see the unsupported area.
You can't think of this system like a normal one with a tiny amount of space around the cartridge in all directions before ignition. Lengthwise there is no space, it has space around the case outer shell. I don't think it will help a whole lot with accuracy to tighten up the chamber diameter because the cartridge is already held steady and consistant in the chamber.
This system of no lengthwise gap or space is so that at ignition there is a gas seal already it doesn't develop it just gets better for a period of the delay. The case can expand in circumference at ignition and press the coating onto the chamber wall. I think the coating is used to control slide barrel movement, sort of the lock delay in some way. Anyway this is a very subtle system unlike anything to date. I am not sure they had reloads in mind when it was designed. :)
Thanks for all your efforts to explain this round. The original design would not have caused this problem. FN obviously made a change (after all it was only to be a military round) to prevent reloading, or they had problems with ejecting. I was involved very early when the French were deciding to use this rifle. Instead they ended up with the much faster round a real "cracker". If I had a weapon (without being able to reload and develop a faster round, I don't think I will bother) I would fool around with the spring to see what a heavier bolt opr stiffer spring would do for the problem. Since there have been many such sucessful blow-backs in the past, I just don't understand any reason for this design since others are well proved. Perhaps it has to do with it being in combination with the pistol? I used more sophisticated measuring techniques including electron miroscope and I just don't trust that shoulder. It is thin after firing and will only get thinner. It becomes work hardened inviting cracking and/or seperating, but if that problem isn't occuring in say 50,000 rounds of reloads in one gun then I would say go ahead. For me, I guess I will experiment with something else. Good Luck Everyone!

darkgael
08-20-2006, 10:47 AM
I'm not finished with this experiment yet. I have been playing with neck-sizing some cases, as I mentioned in another thread. As of today the cases are on their fourth firing, third neck-size. They still chamber and function properly.
The load is 5.7grs. HS6, 55gr. FMJ, CCI SRP.
Pete

btown02
08-20-2006, 11:11 AM
I'm not finished with this experiment yet. I have been playing with neck-sizing some cases, as I mentioned in another thread. As of today the cases are on their fourth firing, third neck-size. They still chamber and function properly.
The load is 5.7grs. HS6, 55gr. FMJ, CCI SRP.
Pete
I combined it with the original thread so we can keep track of the progress being made.

darkgael
08-21-2006, 07:54 AM
I've retired the cases. They were pretty beat up after firing yesterday. Nicks around the rim, coating coming off (just below the shoulder). Two of the cases had small cracks on the relocated shoulder (on a sized case, it would be the neck).
They shot fine and were as accurate as any of this load.
My belief a this point is that the wear on the cases is a function of the hot load, not the neck-sizing.
I shall be loading up quite a few more neck-sized cases but with a lighter load - probably everything the same but a lighter bullet.
Not to lose sight - I am doing this because I'm lazy - neck-sizing is way simpler than full-length sizing. The issue is function and case life. These initial cases worked just fine for four firings (3 NK). We'll see about case life.
Pete

DWP172
09-08-2006, 07:43 AM
Greetings from Italy....I am a new member and this is my first post...

I hope it could be quite interesting...

BSlacker is right but as I can see he refers to headspace in a different way than other forumists....

in fact there is nothing wrong with the pistol...the shoulder forward movement on firing is due to the delayed blowback design of the pistol and the bottlenecked shape of the case....during the backward stroke of the bolt(..and the barrel hinged by a lever...but not locked to the bolt so at the same time barrel and bolt have different strokes..) there is an excess of headspace when the pressure is quite high...so the shoulder "goes" forward...
We experienced the same "shoulder movement" on firing delayed blowback pistols chambered in 7,65 mm parabellum (your .30 Luger)...more exactly with H&K P9S and MAB P15...on the latter the "shoulder movement" is very influenced by the number of cartridges in the magazine(..because the friction between the top cartridge in the magazine and the bottom of the slide..)...
On a larger scale a similar effect you can see watching 20 mm case fired by the british WW2 hispano aircraft cannon(..blowback with locked breech..)...because during case extraction the bore residual pressure is quite high...and the shoulder is not "in touch" with the barrel chamber.

RE

btown02
09-08-2006, 07:45 AM
Welcome to the forum.

DWP172
09-08-2006, 07:47 AM
Welcome to the forum.

Thanks :)

Clayton Moore
10-29-2006, 03:03 AM
Maybe they had NOT RELOADING in mind..........

hate to say it but civilian users were the last thing on FN's mind when they were developing the 5.7x28....... and for a long time the FiveSeven was "never going to be released outside of Law Enforcement"

and for military or LE - reloading is the last thing on their minds - they get to shoot taxpayer provided ammo....

at any rate - re: the 5.7x28...... as has been said several times already, the cartridge case is the only thing holding the slide and barrel together during recoil...... the inside of the cartridge case is pushed out in all directions (front towards the shoulder, out against the chamber wall, and back against the bolt face) by 50,000 (?) psi.

brass is only so strong, and the bolt / slide only has so much inertia..... as a result - each time you pull the trigger on a 5.7x28 case it stretches.

neck sized only? wont work..... gotta bring the shoulder back

Droshi
10-29-2006, 03:54 PM
Can anyone explain to me the different parts of a necked down bullet? I've tried to look here and on google for diagrams but apparently I'm either not doing something right, or it doesn't exist.

Here is how I imagine it:

---_
--|--| <---- Neck
-/---\ <---- Shoulder
|-----|
|-----|
|-----| <--- Main body? or something like that...probably doesn't matter.
|-----|
|-----|
|-----|
L___| <--- ??


Anyway the besides that I gather the conclusions here are just that you should resize the case (meaning shave the neck down by removing material until it's OAL is the same as factory). Does that mean that the shoulder doesn't deform much?

Also that pretty much means that the case has a short life of only a few reloads...but has anyone figured out any other method that gets it to last much longer?

Right now it seems the biggest cost next to the bullet is the brass in my reloading calculations, which is really what makes this more expensive than it should be.

snw19
10-30-2006, 01:40 PM
---_
--|--| <---- Neck
-/---\ <---- Shoulder
|-----|
|-----|
|-----| <--- Main body? or something like that...probably doesn't matter.
|-----|
|-----|
|-----|
L___| <--- Rim

Anyway the besides that I gather the conclusions here are just that you should resize the case (meaning shave the neck down by removing material until it's OAL is the same as factory). Does that mean that the shoulder doesn't deform much?
Resizing the case tries to get it back to the shape it was before it was fired, so it will fit in the chamber and the neck will hold the bullet.
Shaving down the neck is trimming and done after it's resized.



Also that pretty much means that the case has a short life of only a few reloads...but has anyone figured out any other method that gets it to last much longer?
Anytime you 'bend' metal back and forth it's going to weaken.



Right now it seems the biggest cost next to the bullet is the brass in my reloading calculations, which is really what makes this more expensive than it should be.
Brass has always been the most expensive part of reloading, any caliber. It's reloading because you're reusing the fired brass. You can't expect to use the brass only once and have the cost of your reloads be <$20/100. But again, if your buying your powder 1lb at a time, primers by the 100, etc. you could shave cost there too.

Droshi
10-30-2006, 02:12 PM
Lots of ranges around here give away brass free, or charge a very small fee if they gather it for you. Except no one shoots 5.7 so it's just not around.

Medula Oblongata
10-30-2006, 04:48 PM
Brass doesn't exactly weaken when its worked. It becomes brittle. Embrittlement can be removed by annealing. However because the brass stretches everytime its shot it will eventually become too thin and it will tear or crack. Head seperation at the extractor rebate also becomes more likely with additional reloadings. Case head seperations under pressure are B A D, so its important to inspect your brass after several reloadings to ensure nothing "funny" is noticed such as carbon in areas there shouldn't be, pin holes, cracks or tears, etc.

5.7x28mm brass is fantastically soft and I have gotten 12 - 14 reloads from some cases when I keep the loads mild. Very little trimming is done, and the brass is very close to its resized shape. On hot loads I get 3 - 4 loadings before I toss it in the recycle bin. On the hot loads I have to trim as much as 2/100ths at a time. On my realllllly hot stuff I reload it once and toss it into the recycle bin.

BTW, the area snw19 has labeled the rim is only the rim on a rimmed cartrige. 5.7x28, and in fact with the exception of certain weapons such as the desert eagle that fire revolver ammo, all auto loader ammo is rimless. The area he identified as the "rim" is actually the extractor rebate. Just FYI.

Best regards!

Arky
11-03-2006, 12:33 AM
I've been reloading for over 30 years and I don't like the way my 5.7N chambers rounds either. Just because the round doesn't move in the chamber when the gun is in battery, doesn't mean there is no headspace. Any accurate gun will not let the round flop around in the chamber when in battery. Mine does, so do my machine guns. the chambers are made large so the gun will run when it's HOT. Most machine guns are not noted for being accurate.

Seems to me,this round (and the rifle) was orginally designed to be full auto, so it makes sense the chamger is large. Then FN got the idea to make a pistol for the round. I think (that's the key word, just my opinion) the pistol chamber is the same dimension as the full auto gun. Might be wrong about this.

When I bought the gun, I realized it was just a toy-like the M-16 series. Any pistol that shoots a fast moving bullet like this you can't put a scope on will not be a serious gun. I shoot at 100 yards with a pistol quit a bit and without a scope I am not nearly as accurate as with one.

Seems the only good thing this pistol has going for it is it will defeat body armour at close range. At 3 or 4 feet you don't need much accuracy.

Anyway, the reason I got the gun was to play around with it. I didn't realize it would be so hard on brass. I'm hoping to just be able to neck size and get it to chamber. If not, it's for sale.

Really, this gun and round is the epitome of little bullet and lotsa speed-hoping to do what a big bullet will. It is easier to shoot, very little recoil,and you gots lots extras in the mag. Of course, a citizen doesn't have the financial backing a cop does when they "spray and pray".

I'm not trying to make anyone angry here, just trying to realize what this round is really for.

:machinegu

Droshi
11-03-2006, 01:09 AM
There's been a few articles about the "theory" behind these new weapons that are supposed to replace the MP5 (9mm) with the P90. The FiveseveN handgun came later as solution to pilots and a few other jobs in the military where it would not be practical to carry a SMG type weapon. I forget what this new class of weapons is called, but it's around here somewhere if you search.

Anyway it was never really intended for the civilian sector, so treating the round or the gun as if the "plan" should have been is somewhat inaccurate.

Hard to comment about the "space" issue that your talking about...seems to me that results matter more than a hunch. Personally the 5.7 is the most accurate handgun I've ever shot, so I guess I don't really see the corellation between "space" and inaccuracy. By the way, I'm told (though I don't have any experience) that the AK47 and M16 and other so called "inaccurate" weapons are just fine in semi-auto mode...but as soon as you switch over to full-auto they can't hit the broad side of a barn. May or may not be true, but take it for what you will.

Also I have heard that gun manufacturers intentionally produce that space so that the guns are more reliable in all types of weather and conditions. Mostly because they are marketed to military instead of as a target weapon.

Finally I think if you stick to advice here about resizing the cases and check all your cases and toss any bad ones you'll be just fine with having your reloads feed properly.

btown02
11-03-2006, 05:20 AM
Arky, that's your eighth post and in every post you've managed to slam the weapon or the ammo in one way or another. In your post above it is apparent you know very little about the ammo or weapon, and that you did not come here to learn the facts which are here if you'll just take the time to read them. Enough is enough. We get the idea that you don't really like the weapon or the round, you've made your point. Now move on to something else please. We've heard enough of the trash talk about the weapon and ammo. We like it that's why we are here and talk about it and the ammo. And just so you will know the round and pistol are accurate and shots at long range are not that hard if you do your part.

Medula Oblongata
11-03-2006, 12:19 PM
Arky-

Was there a question posed in your last post?

I find myself becoming of the opinion that you have nothing of value to add to the conversation... I hunt with this pistol and have found it to be extremely accurate. My chamber is very tight. I have not noticed ammo "rattling around" or anything of that nature.

Neck sizing is not an adviseable way to prep this brass for loading. The shoulder moves forward too much.

I am also getting the feeling that you have some ulterior motive with your posts. I would as well recommend that you move on elsewhere. We are here becuase we like, respect, and understand the platform. we do not come here to waste our time defending it against the disgruntled.

If your weapon is substandard, which with all of your complaints, it appears to be, I would recommend telephoning FN and having them fix it. However I have never heard of so many problems with one piece from one person.

And for the record, I DO have a scope mounted on mine... I don't know where you get the idea that its impossible to mount one. Halo Mfg. will have their proprietary mount available soon. Until then you can make your own by adapting one from a different gun to fit. Read the pistol forum for "homemade scope mount" to see how its done.

And stop the whining! :p

mikeyc911
11-03-2006, 02:27 PM
ok, im new to guns in all, and reloading this round would be nice, but my question is since everybody is having trouble with reloading their brass, should i even bother trying to do the same or should i just keep on buying new ammo

btown02
11-03-2006, 02:54 PM
Welcome to the forum. As you can see in the reloading section not everyone is having trouble, but it is not the round to learn how to reload on.

jmz5
11-03-2006, 03:19 PM
Welcome to the forum, mikeyc911.

Coultersmith
11-05-2006, 12:51 PM
Medula,
I have an IOM here, and a buncha boxes of ss192, which doesn't shoot too accurately for me either, though it has spectacular effect on target. The gun appears perfect, everything that should be tight is, and everything that should slide does. I am not sure the cause of the innacuracy, but will surely find and fix it, as I have for tons of other guns. This thing is way too much fun to shoot to do otherwise! And I am very impressed with the design.

As a 'smith and reloader, you can expect me to be posting somewhat on these issues soon -- we should be able to get to the facts. My dies are in the mail...I had made a die that would successully push the shoulder back without crushing anything, but had troubles with shellholders made here not being strong enough, I'd only made them out of 4140 steel, and they pulled out at the rim. Had I more time/energy, I'd try a better tool steel next time.

I'm going to predict that a load can be worked out that doesn't blow the necks forward as much as factory. This is all a timing issue, and sometimes counterintuitive approaches work best. If the pressure's down before that barrel hits the stop at about 1/4" retraction (while the slide continues back), the shells ought to come out fine. We shall see! The "blowing through a straw" nature of this small caliber makes the pressure stay in the barrel longer than in some other calibers, so it will be a challenge with hot loads. I love a challenge.

Looking at this shell, it appears that it has a primer to powder ratio unequalled in other calibers. One might even shoot lead bullets with primer alone. This may cause some unusual behavior with some powders, like the troubles I've heard about with H110. Here I also do fun stuff with HE, and often use certain smokeless powders highly compressed as the "booster" charge in blasting caps. You can indeed detonate some of them. This might be what happened with the H110, if it were a compressed load.

:SS Look forward to some news on how to make this thing really sing!

btown02
11-05-2006, 12:54 PM
Welcome to the forum.

jmz5
11-05-2006, 02:28 PM
Welcome to the site

Coultersmith
11-09-2006, 03:16 PM
Thanks for the welcome, guys! Good forum, and good moderation.

I am currently working on loads that don't work the brass so hard. It should be possible to get the bullet gone and the pressure back down before unlocking occurs. The key word, of course, is "should". With the skinny bore it may just take awhile for the pressure to "leak out" of the muzzle after the bullet is gone.

I have Hornady dies, just bought from Midway. The sizer had a minute scratch, barely visible under 8x mag, that scratched the coating. Fixed that with a miniature buffing tool, and all is well now. The resized brass does fit the chamber lots better than the factory stuff I got. But shoving that shoulder back into place reminds me of the effort needed to resize a full house .308 round from a too big chamber! No way that's good for it. My die has what I think is a little oversize neck expander, and I may get another button and grind this one down a bit.

After trying a range of powders in my quest to get the bullet out without wrecking the brass, I'm thinking neck pull might be a real important factor in letting the powder get going good before motion is allowed, thus getting the bullet out quicker once it starts motion. I can say this, the factory ss192 I have here has the bullet GLUED in, full neck length, not just sealed around the neck. Just try pulling one out!

I notice that after wiggling the primers past the factory "crimp" (actually a staking job) that the once-fired factory brass is already a little loose in the primer pocket. Hope someone starts selling new stuff, so I can use and not abuse it and have it last awhile.

I sectioned a piece of this brass to see what I could see. The part that "hangs out" when chambered seems plenty thick, then it tapers in thickness the whole length of the shell up to the neck, where it's pretty thin. So the shoulders will be easy to shove, I guess, compared to brass with less taper in thickness.

Does anyone have a clue why FN puts that coating on the brass?
Mine seems to shoot ok with some of it gone...

btown02
11-09-2006, 03:20 PM
Does anyone have a clue why FN puts that coating on the brass?

Extraction of the fired cases.

http://fivesevenforum.com/forums/showthread.php?t=389