DPMS AR - 10 Primers Coming Out of the Cases
This rifle is new and he's using new Hornady Match brass in .308. It's happened several times. Why are the primers coming out?
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It is hard to say, without seeing the rest of the case, and measuring it for expansion. However, it could indicate the headspace is a little loose, or he is loading a little too warm. You said he is using Hornady match brass, not loads, which would lead one to believe these are not factory loads, and were stated near or at maximum.
Bottom line, we need to know more information...pictures of the rest of the casings, and what EXACT load these are being fired.
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EDIT 1
I shoot the Hornady 168 grain TAP load, and 168 grain match load in my GAP-10. No blown primer's, but the brass itself, shows signs of being soft.
Best0 -
Let's see:
Blown primer, check
Ejector mark showing, check
Headstamp "blotted", check
Bottom line, he's some 10-15000 PSI over max on pressure.
Tell him to check his loading manual for the recommended charge of the EXACT powder he's using (and not just "close" on the name/number), also his OAL (if you seat into the lands, you need to limit your charge to 90% of the book numbers).
Finally, will a bullet easily fit into the mouth of a un-sized case? It's rare, but he might have a neck clearance issue also.0 -
I think you are loading way to hot, the brass appears to be flowing into the ejector slot. Could be bad brass, that someone annealed the heads.
Don't shoot anymore of that lot. May want to consider a trip to a good gunsmith.0 -
I did say it wrong. He's using new Hornady Match ammo. Not reloads. I'll get the rest of the information when he calls me. 0 -
IMHO, before he does anything else, try other different brands and loads of factory ammo.
Some of the ammo that is loaded to be optimal in BA rifles, might have problems with semi-autos. That have looser bolt headspace and chamber tolerances.0 -
First of all, did he leave his ammo out in the sun? This can raise pressures.
I had a new vanguard show some brass flowing into the ejector on factory ammo.
I would say some tolerance is too close rather than too loose. If the case head had too little support it would not have extruded the brass into the ejector or ironed out the headstamp because pressure would have been lower, not higher.
I have an MAS36 which has a slightly oversize chamber. It bulges the cases too much to enter the resizing die but with no signs of excess pressure on the case head. My rifle doesn't loosen primers but a different case head with inadequate support MIGHT expand enough to let the primer loose, because maybe the Federal match loads are heavier than my reloads were or maybe my brass is harder, but there would be no extrusion of brass into the ejector because pressure would be lower than normal, not higher.
Or maybe he didn't clean all the lube out of his chamber. The case needs to be able to expand just a bit. The powder charge is calculated with that in mind.
Excess headspace would lower rather than raise pressure. The case would have room to stretch. Unless the chamber was oily or greasy, (which is a definite possibility,) all the stretch would occur where the case wall meets the case head and there would be a ring of thin brass you could feel with a paperclip or allen wrench stuck into the case.
Maybe they didn't control the chrome lining process enough and the barrel and chamber are too tight. Does it chamber rounds freely? It's hard to believe match ammo would require more clearance for safe pressure than that, because it's probably intended for close-fitting barrels and chambers. Or, if the neck was cut a bit short, it wouldn't let the crimp open freely, but I'd think you'd see signs on the case. Maybe this model is not chrome lined like milspec guns are and the barrel was cut a bit rough or they left some burrs in there.
It would be a shame to go through too much of a hassle just because the bore was left a bit rough. It might just need a few rounds put through it. Can you slug a barrel?
Of course, there's a chance he left something in there like a patch. How many rounds did he fire?
I would fire one more shot after a good cleaning with copper solvent, and carefully and thinly oiling the bore then wiping the chamber dry. Make sure the ammo is at room temp. If it still shows pressure signs, it's time for a gunsmith or a return to the manufacturer.0 -
quote:Originally posted by SoreShoulder
First of all, did he leave his ammo out in the sun? This can raise pressures.
I had a new vanguard show some brass flowing into the ejector on factory ammo.
I would say some tolerance is too close rather than too loose. If the case head had too little support it would not have extruded the brass into the ejector or ironed out the headstamp because pressure would have been lower, not higher.
I have an MAS36 which has a slightly oversize chamber. It bulges the cases too much to enter the resizing die but with no signs of excess pressure on the case head. My rifle doesn't loosen primers but a different case head with inadequate support MIGHT expand enough to let the primer loose, because maybe the Federal match loads are heavier than my reloads were or maybe my brass is harder, but there would be no extrusion of brass into the ejector because pressure would be lower than normal, not higher.
Or maybe he didn't clean all the lube out of his chamber. The case needs to be able to expand just a bit. The powder charge is calculated with that in mind.
Excess headspace would lower rather than raise pressure. The case would have room to stretch. Unless the chamber was oily or greasy, (which is a definite possibility,) all the stretch would occur where the case wall meets the case head and there would be a ring of thin brass you could feel with a paperclip or allen wrench stuck into the case.
Maybe they didn't control the chrome lining process enough and the barrel and chamber are too tight. Does it chamber rounds freely? It's hard to believe match ammo would require more clearance for safe pressure than that, because it's probably intended for close-fitting barrels and chambers. Or, if the neck was cut a bit short, it wouldn't let the crimp open freely.
It would be a shame to go through too much of a hassle just because the bore was left a bit rough. It might just need a few rounds put through it. Can you slug a barrel?
Of course, there's a chance he left something in there like a patch. How many rounds did he fire?
I would fire one more shot after a good cleaning with copper solvent, and carefully and thinly oiling the bore then wiping the chamber dry. Make sure the ammo is at room temp. If it still shows pressure signs, it's time for a gunsmith or a return to the manufacturer.
This is not Match AMMO the only thing factory match about it is the brass so he's basically shooting reloads.
EDIT I stand corrected.[;)]0 -
I had a CUP system made for .223 in the '80s and ran pressures up to 70+KPSI CUP. The fixture is designed such that primers can't pierce or blow out.
At that pressure, primers became loose.
I have also had some Norma brass with soft heads that took impressions
in the 30-40KPSI range.
Also, in pistol pressure range, I essentially obliterated case head markings on IMI 41Action Express,again, soft brass.
Your problem is far too much pressure for that case, either because brass is too soft, loads are too hot, neck chambering is too tight, Bullets oversized for bore.
I'd start by contacting both rifle and ammo manufacturers and lay it on them. You shouldn't have to figure it out or work around a problem of their making.0
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