Blown Primers

[RWF]

the wife and i went to a rifle side match, and shared a 200 round of the black and white box of XM 193. i not nornally use any thing 5.56. but it was cheap. the wife's AR ran great and mine kept blowning primers. both are 16" guns hers a 1 x 9 carbine gas system with a JP gas block with a factory bolt that i had milled for some wieght loss. mine is a 1 x 7 mid lengh with the JP gas block and LMOS carrier. both use a standard buffer spring and buffer.

any idea's?

note this the same gun i have always used, at blue rigde, benning, etc.

thanks

also when we got home i made sure the chamber and barrel were clean up "no primer parts" then loaded 2 mag with every kind of ammo i had but 5.56. 55 62 69 & 75. it ran great.

both have 5.56 chambers

Edited April 7, 2011 by RWF

[whistlepig]

sorry to ask, but blown primer as in the round discharged and the primer came out of the case, (little sumbit*# usually ends up under the trigger mechanism) or blown as in stayed in place, but ruptured and spewed gas back at ya? Two different issues. Off the top of my head, inspect your firing pin tip carefully. A chipped one can contribute to pierced primers and I actually have seen a piece of trash lodge in the firing pin hole and cause it as well.

Ammo good? If you have any of that box left over, inspect them close and guage em.

[RWF]

the primers where coming out of brass in one peice, even found one on top of the mag follower. like it just fell out. but like i said me and the wife where useing the same 200 round box and she had 0 failures

Edited April 8, 2011 by RWF

[RiggerJJ]

bullets engaging the rifling when the round was seated, causing over pressure??? A light carrier/buffer may show this earlier than a standard weight system...

maybe check a round in the chamber & see if it's bullet gets "stuck" in the rifling.

just a thought...I may be way off thou.

jj

[Alaskapopo]

the wife and i went to a rifle side match, and shared a 200 round of the black and white box of XM 193. i not nornally use any thing 5.56. but it was cheap. the wife's AR ran great and mine kept blowning primers. both are 16" guns hers a 1 x 9 carbine gas system with a JP gas block with a factory bolt that i had milled for some wieght loss. mine is a 1 x 7 mid lengh with the JP gas block and LMOS carrier. both use a standard buffer spring and buffer.

any idea's?

note this the same gun i have always used, at blue rigde, benning, etc.

thanks

also when we got home i made sure the chamber and barrel were clean up "no primer parts" then loaded 2 mag with every kind of ammo i had but 5.56. 55 62 69 & 75. it ran great.

both have 5.56 chambers

What is the barrel maker. I have seen this issue with DPMS barrels that were supposed to be 5.56 chambers but weren't.

Pat

[whistlepig]

Due to your rifle having a normal history, i would chalk that one up to ammo... Maybe primer pockets at the high end of tolerance, maybe not crimped. The newer brown box XM193 brass and primer comes off the same line as the militay/govt line and have a crimped in primer. im not sure about the white box. I know its weird since she didnt experience it, but stranger things have happened. It would be interesting to mic fired cases from that box of ammo from the two rifles and compare results.

[assaulter]

If you can get access to a chronograph, check a batch of ammo in both rifles and see if yours gets a higher velocity. It may indicate your rifle producing higher pressure.

[slowsure]

let the wife shoot that ammo. Your not shooting suppressed are you?

[RWF]

no this was not my suppressed gun it was my race gun that i have used every where. i did not look at any of the brass my wife shot but most of mine did show signs of over pressure in most of the brass that i found that i knew was mine.

i have already told the wife all the 5.56 ammo is hers.

the barrel is CMMG chrome lined 1 x 7 mid lengh 16" with a 5.56 chamber.

i will try and chrono both guns tomorrow and post what the results are.

thanks

[VegasSean]

I would take a caliper and measure some rounds before and after chambering. Don't fire, just chamber and eject. Also, inspect the rounds when you eject them.

[RWF]

here is the chrono info

mine wife's

3341 3115

3292 3115

3292 3072

all are F.P.S.

i was very suprised at how different the 2 16" barrel are.

hers is a TAC-2 briefcase gun with a YHM 16" 1 x 9 carbine length

mine a CMMG 16" 1 x 7 mid length.

all ammo is from the federal 5.56 from the 200 round box that i had the issues with.