Why does the Military crimp primers?

[general_purpose]

I noticed that the M118 and the Military 5.56 ammo have crimped primers, either in the form of a round ring around the edge of the primer cup, or by three dimples around the circumference of the primer cup. I don't see civilian rounds with these.

Are these crimps there to keep the primers in their cups or is there another purpose for these crimps? Do military rounds have higher pressures? I can imagine if, say on a 5.56, the primer or parts of a primer blew out and the fragment fell into the bolt carrier or the fire control assembly in the middle of a firefight, that would not make for a pretty after action report!

 

[jasonk]

Re: Why does the Military crimp primers?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: general_purpose</div><div class="ubbcode-body">
Are these crimps there to keep the primers in their cups </div></div>

Yes, not the pressures of the rounds but the inertia caused by full auto fire I believe.

 

[PLeighton]

Re: Why does the Military crimp primers?

Actual M118 does not have a crimped primer.
All military 5.56mm does have the crimp and all 7.62mm except M118 & M852 have the crimp.
They also do not have a crimped in bullet either.

jasonk is correct.
The crimp is there to keep primers from becoming dislodged during the cycling of the weapon.
This is not exclusive to full auto fire though.
AR platforms are notorious for dislodging primers while firing in semi-auto.
This is illustrated by the new Mk 316 Mod 0 cartridge.
http://www.snipershide.com/forum/ubbthreads.php?ubb=showflat&Number=1178282
It is similar to M118, but uses a crimped in primer & different powder.
The addition of the crimp is due to the rise of the AR10 / SR25 type SWS.

 

[CavalrySoldier3ACR]

Re: Why does the Military crimp primers?

Dr. Phil is absolutely correct in his explaination of why the military crimps primers. The military is only concerned with consistent functionality in combat. The expectation is that the brass will be left on the battlefield with no consideration for reuse. When brass is collected at the firing range, it is returned to the supply system and weighed to make sure what was issued was used and not pilfered. It is then sent for melting and recycling. It is never designed with the intention of reloading.

 

[HillbillyfromAL]

Re: Why does the Military crimp primers?

It's also cheaper than using primer sealant.

 

[Bacarrat]

Re: Why does the Military crimp primers?

Have you ever picked up XM193 right after its fired? Flat primers and ejector swipe on just about all the cases out of my M4. I could only imagine what would happen if they werent crimped from the LC plant.

 

[Cowboy]

Re: Why does the Military crimp primers?

If the AR situation is that bad, are civilians doing something different when they reload for it?

 

[Grump]

Re: Why does the Military crimp primers?

"Why does the Military crimp primers?"

To piss YOU off.

 

[JRose]

Re: Why does the Military crimp primers?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Grump</div><div class="ubbcode-body">"Why does the Military crimp primers?"

To piss YOU off. </div></div>

ROFL....

 

[Rovieairto]

Re: Why does the Military crimp primers?

Also ammunition that is used at elevated temps tends to have elevated pressures that could blow primers.
A round left in a hot chamber (like 450+ deg F hot) and then fired would likely create excessive pressures and the fire control mechanism can become all jammed up with a single blown primer.
This is a typical military scenario for their ammunition.
The open bolt belt fed weapons (M-240, M-249) could probably function fine without crimps but the ammunition sitting out in the sun on a 130 deg. F day could easily break 200 deg. leading right back to the original problem.

This is why I believe that they crimp their ammo. That and to piss off reloaders.

 

[Queequeg]

Re: Why does the Military crimp primers?

<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">That and to piss off reloaders. </div></div>

Doesn't piss me off. It's the only time I can pick up brass on the range that wasn't mine and KNOW it is once fired.

I don't care about no steenkeen creemps

 

[MitchAlsup]

Re: Why does the Military crimp primers?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Cowboy</div><div class="ubbcode-body">If the AR situation is that bad, are civilians doing something different when they reload for it? </div></div>

99.4% of civilian shooters are not going fully automatic.

In addition, If a primer does come out and get stuck in the firing mechanism, it is not a life threatening situation.

 

[Guest]

Re: Why does the Military crimp primers?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Rovieairto</div><div class="ubbcode-body"> The fire control mechanism can become all jammed up with a single blown primer.</div></div>

It will land in the bolt locking recess, on a M16 style weapon, an is a bitch to clear quickly. Immediate action will not work on this issue.
In a M14 it will land in the mag an get kicked to the bottom of the mag, then when the last round is entering battery it will jam in the lower locking recess. Just turn the weapon upside down an apply immediate action.
M60, it will normally get kicked out with the links.