Subsonic loads go unstable only with can

Reloading info for the 5.7x28mm

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mxgobig
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Subsonic loads go unstable only with can

Post by mxgobig » 13 May 2014, 06:22

Just like the title says, my subsonic loads look great...
They cycle the slide. Are stable at 15 yards. Are subsonic.
Until I screw on the suppressor... Then the keyholes start.
Has anyone seen anything like this

Here are the details:
Fiveseven pistol
1:8 twist barrel (yes I know 1:9 is standard)
Multiple bullets and manufacturers from 55gr to 69gr
Multiple powders
SWA spectre II suppressor (no baffle strikes)
Velocities are all around 950 to 1050
Barrel is true and functions fine
Threads are straight and true also
Everything is tight.

I know the bullets I'm trying are heavy, but I don't understand why the appear to stabilize without the suppressor.

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panzermk2
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Re: Subsonic loads go unstable only with can

Post by panzermk2 » 13 May 2014, 09:04

Above 55 you are really sticking your own neck in a noose.

How do you know for a fact you are not having baffle strikes?
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mxgobig
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Re: Subsonic loads go unstable only with can

Post by mxgobig » 13 May 2014, 09:40

I disassembled the suppressor and inspected the baffles...
No marks or dings at all.

I understand that even with the faster twist barrel that these may not work.
I am just trying to understand why I don't get any signs of instability with the no suppressor.
Last edited by mxgobig on 13 May 2014, 15:54, edited 1 time in total.

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panzermk2
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Re: Subsonic loads go unstable only with can

Post by panzermk2 » 13 May 2014, 10:13

I still think you getting a strike. Sometimes it is very hard to tell.
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mxgobig
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Re: Subsonic loads go unstable only with can

Post by mxgobig » 13 May 2014, 10:51

First, panzer thank you for your input.
I appreciate the help.

I found this on another forum... and I am running an adapter on the spectre that might be putting the muzzle closer to the first baffle. I will have to measure tonight to check.
What do you think of this?

"Keep in mind that some .22 rifles have 1/2x28 threads that are too long (like the M&P-15 .22) and the suppressor either doesn't properly shoulder or it shoulders but the the crown is too close to the first baffle. If the suppressor doesn't shoulder properly it will be misaligned and you can get baffle strikes. And if the suppressor shoulders but the bullet exists the barrel too close to the first baffle, it can cause the bullet to be unstable and you could get baffle strikes. (I saw this happen with a Spectre II on a M&P 15 .22; the baffles on a Spectre 2 are asymmetrical, and the fact that the bullet exited too close to them cause it to keyhole in the target. Luckily there were no baffle strikes.) But this is all easy to fix with a $10 spacer like the one from Gemtech."

Again, thanks for the help.

DoubleJ
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Re: Subsonic loads go unstable only with can

Post by DoubleJ » 13 May 2014, 16:01

I'd think any spacer would help for the time being, even a crush washer or something, to see if that's your issue. Keep us informed, I've just started playing silencers myself and I'm in the market for either a Sparrow or an Axiom.

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Re: Subsonic loads go unstable only with can

Post by bruteandbear1 » 14 May 2014, 04:38

Just like jay said anything under 55 grains is really unstable. I Would Use Some 50 Grain FMJ's If You Can Find any. If Not Stick To 55 Grain Max And Dont Go Over Because You Will Have Performance Issues, best Of Luck Let Us Know What U Find Out.

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Re: Subsonic loads go unstable only with can

Post by Buffman » 14 May 2014, 08:31

you should only use shims if you want to move it out. Crush washer may make the suppressor and or adapter non concentric to the barrel.

shopsmart
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Re: Subsonic loads go unstable only with can

Post by shopsmart » 17 May 2014, 04:42

I have first hand experience with this kind of problem. If you look on the other forum my PS-90 sbr / silencer story is somewhere over there. The posted above 1/2x28 info is true. Our 22 cans are .4 depth of threading while alot of mounts are .6 depth. There are .2 spacers out there. Just do a google search and you can find a 3 pack for $20. Yes it is close to the first baffle, but it is the blast chamber that is part of the problem. Gases might be throwing off the stablity.

The other part is baffle strike. Mount the supressor, look through. If you see any baffles, congrats, you have someone to yell at. The other is look VERY carefully for any slight crescent moon. You can do this by moving left right up down the barrel in your eye sight. See any imperfections? Congrats you have someone to yell at.

Hope that helps.

Oh yeah, 62 grain pills are possible, but noose yes. However FN looks to have transitioned their subs to 62 grains. Some people are investigating, but months and months out as far as research or actual subs in hand I imagine.

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Re: Subsonic loads go unstable only with can

Post by panzermk2 » 17 May 2014, 11:39

The 62gr was a prop round and fake. It was made for a show.

62gr will never stabilize out of the FsN.
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mxgobig
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Re: Subsonic loads go unstable only with can

Post by mxgobig » 20 May 2014, 17:48

Looks like it was the muzzle too close to the first baffle.
Things started to come out of the can a lot better after I corrected the spacing.
60 grain v-max may still be on the heavy (long) side... I think I'll take Jays advice and try 55s...
Thanks for the help!!!

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Re: Subsonic loads go unstable only with can

Post by panzermk2 » 20 May 2014, 21:12

Glad we got things sorted.
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GONRA
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Re: Subsonic loads go unstable only with can

Post by GONRA » 15 Aug 2018, 07:27

“Good ‘n Bad News” Info that may (or may not) be interesting to some of ya’ll:

GONRA’s FN FiveSeven pistol, EA threaded barrel / recoil spring assembly,
Gemtech suppressor, handloads using FN and EA brass, etc.
>>> CCI #500 SMALL PISTOL primers, 55 gn. FMJBT bullets. <<<

Modest 3.0 grain Bullseye powder charge loads with fresh “used as is, NO ADDTIONAL CASE LUBE”
5.7x28 07 EA brass CASES functioned OK but had several fired cases with BODY SPLITS.
(Never saw any BODY SPLITS in quite a bit of resized FN Scharch brass reloading. ???)
Bad News: Bullet went unstable in suppressor.

Assume it’s a message to NOT use Bullseye in this caliber? ???
Cases were bulged, primers eyeballed Just Fine….

3.8 grain HS-6 powder load in resized FN Scharch brass functioned Just Fine
Bad News: Bullet went unstable (keyholing) thru suppressor.
5.0 grain HS-6 powder load in resized FN Scharch brass functioned Just Fine
Good News: Bullet traversed suppressor (NO keyholing) Just Fine.
>>> POSITIVE illustration of “spin it up to (hopefully) get stability, survive suppressor”. <<<

4.5 grain HS-6 powder load in fresh 5.7x28 07 EA brass
(thiiiin coat STP Oil Treatment rubbed onto case body to mimic my resized FN Scharch brass ,
reduced powder charge for smaller EA case capacity) functioned Just Fine.
Good News: bullet traversed suppressor (NO keyholing) Just Fine.

Yup, its NOT a “subsonic load” but will load some of this ammo for Generalized Blasting…….
(As you can imagine, havalotta BAD NEWS loads that are NOT included here.)

+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

Next step is to seek a subsonic load with 50 grain Hornady SP bullets per panzermk2 suggestion.
Load up 4.5 grain HS-6 powder charge in fresh 5.7x28 07 EA brass
(thiiiin coat STP Oil Treatment rubbed onto case body) .
Assuming bullets traverse suppressor OK will then load powder charge DOWN in 0.1 grain increments, until bullets “go unstable” thru suppressor.
With that data, hope to verk up a POSSIBLE subsonic load for my pistol.

By starting at the top and verkin’ down,
won’t drive myself nuts seeking something that’s never gonna happen.

GONRA
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Re: Subsonic loads go unstable only with can

Post by GONRA » 25 Aug 2018, 13:17

GONRA’s FsN pistol. Gemtech suppressor, EA barrel heavier recoil spirng 9 yard shootin’ experiments with 10 rds.
EA brass, 50 grain Hornady SP SX #2240 bullets, CCI #500 pistol primers.
Started off with 4.5 grains HS-6 powder.
Everything still functioning just fine. Still have “no keyholing”.

Now down to 3.8 grains HS-6.
(Adjacent shooter thought I was shootin’ squibs, so Gemtech is functioning great!)

Use “olde fashioned” one hand bullseye stance.
Had 8 shots in nice 1+ inch group, 2 (apparent) flyers 3 inches from center of group.
(At my age must assume these “flyers” are just ME screwing up – NOT REALLY “flyers” -
but have no way of knowing for sure.)

BUT – just for the hellava it, have any of you “super really careful shooters”
ever noticed such a “onset of instability” when carefully investigating these issues?
(We all know keyholing WILL begin as powder charge is further reduced.)

Pleeze lemmeno. THANX!

cav2108
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Re: Subsonic loads go unstable only with can

Post by cav2108 » 01 Jan 2020, 17:13

Those bullets you are trying are maybe just too long for 1:9 twist. Berger has a calculator you can use to research that at https://bergerbullets.com/twist-rate-calculator/

More grain weight at the 900-1100 fps subsonic velocity is more worthwhile than a lighter bullet at the same velocities. In 1:9 twist barrels, a bullet length over 1.00" is unlikely to be stable at any distance, and to be really stable should probably not be longer than 0.900", but use Berger's calculator to get some idea of stability before you bother to load whatever bullet you are considering. Polymer-tipped bullets are longer than non-tipped bullets of the same weight. Long enough to be unstable sometimes.

USE CAUTION: The loads that I am sharing here are okay in my guns using FN and Federal AE brass. I haven't tried any of the smaller capacity Elite Ammunition cases at all. So, work up from a bit lower charge weights and be alert for a squib bullet getting lodged in your barrel - if you didn't see an impact or hole in the target or you didn't get a chronograph reading for the shot, then you need to make sure there isn't a bullet lodged in the bore before firing the next shot. Just because the slide went back, ejected the case, and fed the next round from the magazine DOESN'T mean that the bullet left the barrel !! Ask be how I know. And a new FiveseveN barrel is a bit more than $400 bucks even if the pistol itself is still okay, eh?. Use a beam scale. The digital ones can often vary more than a tenth of a grain either way because the round up or down to the nearest tenth. That's not accurate enough for 5.7x28 reloading.

I usually get 5-8 reloads out of a case and usually only retire them because the coating has pretty much worn off. I've been reloading 5.7 since 2011 and other stuff since 1970. I regularly reload everything from 27g pulled SS198 bullets up to 77g SMKs. I prefer TrueBlue, AutoComp, and VihtaVouri N340 powders for 5.7.

I regularly shoot 77g Sierra OTM SMK bullets for subsonic velocities and the version of that SMK with a cannelure #9377GT seems to produce the best but still marginal stability. (This is NOT the #9377T which does NOT have a cannelure although it seems to be stable at 50 yds (clean holes in paper) but is 0.990" in length). The #9377GT are 0.976" long. I also tried some pulled 77g that look a bit like the SMKs but are not SMKs (different ogive) that is 1.009" long but was not stable at 50 yds (they work great in a 1:7 twist .223 Rem though).

In my initial testing 3.0 grains of TrueBlue gave an average velocity of 814 fps, 3.3 grains gave 1054 fps, and 3.5 grains gave 1180 fps average velocity. I settled on the 3.3 grain load as my favorite subsonic 5.7 loading. With the SMK # 9377GT and the bullet seated to a C.O.A.L. of 1.581" and each cartridge checked in both Sheridan and Elite Ammunition gauges.
The Sierra #9377GT bullets are stable at 100 yds and produce consistent 3 inch groups at that distance. Very good terminal results on large armadillo at 25 to about 60 yards.

I also have a load that works subsonically in the FiveseveN pistol at 1020 fps, but is supersonic in the PS90 at 1299 fps. That load also uses TrueBlue powder and a 68g HPBT from Hornady with a cannelure #2278C, seated to a C.O.A.L. of 1.584", and using 3.6 grains of TrueBlue powder. It is listed as being marginally stable in 1:9 barrels due to its length of 0.914" and probably different center of mass compared to the 77g SMKs which are actually a bit longer bullet length.

The 77g SMK is very accurate in the PS90 and still subsonic. All these loads are very quiet, although I haven't tested any of them with a suppressor. Neighbors were not disturbed by the single pops on armadillos without a suppressor. My wife, inside the house said she barely heard anything even thoug she was standing at a closed window, She said she wouldn't have noticed the noise at all if she hadn't been expecting it. I actually like armadillos, but the wife won't abide them digging up the yard.

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