5.7x28mm reloading series final episode

Reloading info for the 5.7x28mm

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jkelley209
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5.7x28mm reloading series final episode

Post by jkelley209 » 05 Jul 2015, 15:41

https://www.youtube.com/watch?v=r5M8KFG0dto" onclick="window.open(this.href);return false;

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panzermk2
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Re: 5.7x28mm reloading series final episode

Post by panzermk2 » 06 Jul 2015, 09:41

Move your chrono out to 15 feet.

The thermal cloud from the muzzle blast was contributing to your issues even more then the low light. FYI bullets are still accelerating out to about 10 feet. I have posted on this phenomenon before.


Also if you plan on doing more testing with the 5.7 moving your chrono out will extend it's life. The blast from the 5.7 is such that after time it will scramble the guts of your chrono.


This posts talks about Chronograph issues.

http://www.fivesevenforum.com/viewtopic ... ronographs" onclick="window.open(this.href);return false;
Jay Wolf
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jkelley209
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Re: 5.7x28mm reloading series final episode

Post by jkelley209 » 06 Jul 2015, 10:19

Thanks Jay, When do you think i can get the quickest turn around time on a trigger job. what time of year.

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Re: 5.7x28mm reloading series final episode

Post by panzermk2 » 06 Jul 2015, 11:18

Now.

There is a drop off around Christmas but with our in house brass project going on line in Nov there won't be a gun touched until Feb.
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jkelley209
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Re: 5.7x28mm reloading series final episode

Post by jkelley209 » 06 Jul 2015, 11:22

whats the turn around time now?

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Re: 5.7x28mm reloading series final episode

Post by panzermk2 » 06 Jul 2015, 11:31

About 3 weeks.
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Re: 5.7x28mm reloading series final episode

Post by panzermk2 » 06 Jul 2015, 11:32

Unless night sights are also added and we don't have them in stock ready to go.

If it's a MKI we plenty in stock.
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Re: 5.7x28mm reloading series final episode

Post by jkelley209 » 06 Jul 2015, 11:52

it's a mark 2 but im just looking at trigger job and accurizing

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Re: 5.7x28mm reloading series final episode

Post by panzermk2 » 06 Jul 2015, 12:49

3 weeks
Jay Wolf
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jkelley209
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Re: 5.7x28mm reloading series final episode

Post by jkelley209 » 06 Jul 2015, 13:33

Thanks Jay I'll get it to you quickly

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Re: 5.7x28mm reloading series final episode

Post by DoubleJ » 06 Jul 2015, 18:25

panzermk2 wrote:... FYI bullets are still accelerating out to about 10 feet. I have posted on this phenomenon before...
Link please

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Re: 5.7x28mm reloading series final episode

Post by panzermk2 » 08 Jul 2015, 14:14

The original goes farther back but the first I found was me quoting me concerning the referenced post.


panzermk2 wrote:You missed the big write up I posted. The bullet is still inside the expanding gas plume. The plume is traveling faster then the bullet. There is no atmosphere for the bullet to push against to slow down in fact the plume is dragging the bullet faster.


panzermk2 wrote:I can shoot the same lot of ammo through the same gun. Every thing can be identical including the shooter except for one day apart. Temp and humidity the same since I have that controlled in the shop and our indoor range.

You know what? There will be an 100 to 200 fps difference sometimes.

Also measuring at the muzzle, if you can get a reading, gives you lower velocities. The bullet is not done accelerating until well after it has left the barrel.

Also factor in the variance in equipment. A $300 dollar chrono is no where as consistent machine to machine as a $3000 chrono.

Now as to why the above difference of 200 fps or sometimes it's 20 fps?

I asked this myself and discovered the answer in one of my 100 year old ballistics manuals.

Barometric pressure. So now when we load ammo it's test lot has all the standard data including BAR written on the box. When the ammo is tested the BAR at the range is also recorded. I have started, mind you STARTED, working on the correlation in fps change and BAR. In fact when some of my 10mm was tested by that third party the velocities he got where consistently HIGHER then any I had ever gotten including with the test loads from that run of ammo his samples came from.

Now here some really good reading from the creator of my primary pressure testing system when we where discussing what a pain in the ass it is to measure 5.7x28 velocities accurately.


Understand rifle/handgun velocities listed as "Muzzle" are usually taken 10+ ft from the muzzle.
This is the industry standard and even described in SAAMI protocols. Shotgun data may
be 5 ft. and real big bores to 15 or 20 ft. The data is never actually collected at the muzzle.

Since the advent of good radar range instrumentation it has been known the bullet continues
to accelerate 8 to 12 inches after exiting the muzzle. More importantly, the bullet exits
with venting gas and does not begin to decelerate until it punches out of the gas plume as far
as 4 to 6 ft. from the muzzle.

Image

The above shot taken in a vapor chamber clearly shows venting gas, the shock cone where air drag
starts, etc. Only when a bullet punches through the venting gas will air drag cause velocity
erosion. Those software products that attempt to back up velocity to the muzzle from
chronograph screens are bogus and entirely miss this physical phenomenon
.

The bottom line is even if erosion starts at 4, 6 or 8 ft. with screens at 10 ft; the
slight error is less then the instrumentation error that can be expected from light trap
chronograph technology and certainly less then the ambient temperature affect on propellents
or normal shot to shot deviation. Since the point where velocity erosion begins can only be
learned on a radar range, the industry has adopted standard screen spacing.

The venting gas in the above shot contains allot of heat. All chronograph sensors read into the
IR spectrum so the hot gasses only serve to blind the first sensor.
Jay Wolf
Pr. Elite Ammunition

"Engineers, the oompa-loompas of science!"

Be'ein Tachbulot Yipol Am Veteshua Berov Yoetz
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Kiran04
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Re: 5.7x28mm reloading series final episode

Post by Kiran04 » 14 Aug 2015, 05:37

Is this going to be your defensive load?

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