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9/22/2017 12:11:25 AM
Posted: 9/8/2005 1:26:54 PM EDT
here are a couple samples of some spent brass that was damaged. i've seen a few examples of each, but not enough to make me significantly worry. still, i'm curious as to why this might happen.

the ammo is XM193, 2004 production. rifle is an LMT 14.5" upper /w standard bolt group. upper had around 400-500 rounds on it when these samples were collected.

it may be relavent to note that the rifle continues to give me FTE's. there are about 600 rounds on it now, and it has an o-ring on the extractor spring (which helped a lot, but not completley). the lower is a preban PWA and the 4 pos stock has a standard buffer, i believe.

the left one is crushed on both sides, but slightly less on the side i didnt take a pic of.

Link Posted: 9/8/2005 1:47:38 PM EDT
Failure to extract?
Failure to eject?

some of the cases look like they have had a failure to feed and look like they have damage/gouges from the bolt lugs and/or the barrel extension lugs.

describe the failure more specifically please.
Link Posted: 9/8/2005 2:15:38 PM EDT
the failure to extract problem is that spent brass gets stuck in the chamber and the extractor slips off. the bolt then tries to feed another round... usually the tip of the bullet gets jammed between the rim of the stuck brass, and the mouth of the chamber. to clear it, i have to drop the mag, put my fingers up the mag well and flick the jammed round loose, it wont fall out just from shaking or smacking the rifle. then i recock the charging handle, and then manually pull on the charging handle to extract the spent round.

after i put an o-ring on the spring, and got a chamber brush, the rate of failure dropped a lot, but still occurs about 20% of the time.

i wasn't thinking that this damaged brass issue is related to the FTE, but i usually take those jammed rounds and put them back in the mag and try to feed them again because i dont see any noticable damage besides scratched copper on the jacket... maybe they got weakened from being slammed into the back of the spent round? that could explain the dented case, but what about the ripped neck one?
Link Posted: 9/8/2005 7:16:05 PM EDT
You have a over-cycling problem.
To correct, use a heavier buffer.

Note on dents,

Rear dent towards the rim, case hitting the back of the ejection port, and causing the damage.

Center dent, rifle short cycling/bolt over,and the bolt grabbing the case at the center and not the rim. This causes a dent that start shallow on the center of case, then sharp towards the neck.

Overcycling, the case is slung with so much force at end of cycle that it is beyond bounced off the case deflector. Read the back edge of your deflector is missing all the anodizing. The other side dent most likely was cause by what ever the case hit after being bounce free of the ejection port.

As for the blown mouth on the case shown upper right, welcome to the world of XM-193 (read the X means that this ammo can not be sold to the military due to defects in military standards). My guess is that the case has a cracked mouth and you missed it when you were loading mags.
Link Posted: 9/9/2005 7:39:11 AM EDT
wow, thats some pretty detailed info dano, i'm gonna have to snag a heavy buffer after i finish my move (going from PRMA to TX next week). dunno how long its gonna be before i get the chance to go shooting though
Link Posted: 9/10/2005 3:58:53 PM EDT
[Last Edit: 9/10/2005 4:02:10 PM EDT by Dano523]
Also, if your going to shoot XM-193 you really need to check the rounds as your loading them into the mags for defects. Like stated, the one case with the blown mouth had either a cracked or dented mouth and should of never been fired.

And for the record, I really like M-193, it's the reject Xm ammo that is not up to military standards that I have a problem with (read the military buys m-193 cheaper that what we pay for the xm ammo, so you do the math).
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