I was trying to verify my AR-10 zero using Hornady Superperformance 165 SST ammo once I arrived in Florida for a hog hunt. At home in Maryland if was shooting great. I went to shoot 5 rounds just to confirm everything was still good from the trip down and I was all over the place. Couldn't hold an 8 inch group. Recoil felt different as well. I grabbed the brass to put back in the box and noticed I had cratered primers on 3 cases and 2 with pierced primers. I actually thought I had a piece of my firing pin broke off in the last case fired. What is causing this in factory ammo and what can I do to prevent it from happening again? I ended up going to a local store and bought 4 boxes of Hornady Precision Hunter 175 ELDX. I bought one box to try then went back and bought three more for the hunt. I have not had any issues so far. I could understand if they were hot reloads but was surprised that factory ammo would have pierced primers like that.
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Pierced primers in AR-10
- Thread starter Maelstrom
- Start date
What type of bolt? When I built mine, mostly everyone recommended using a high pressure bolt with a smaller diameter firing pin channel.
This was copied from another site.
The term "high pressure" I think is just a way JP distinguishes their small diameter firing pin bolt from bolts with traditional size firing pins. If you read their site they list this warning:
"WARNING: The JP .308HP bolt does not allow for the use of excessive pressure, overloaded ammunition that exceeds SAAMI specifications. When evaluating new ammunition, always start on the low- to mid-range of any published load data and work up. A good indicator of working pressure is the primer retention on the subsequent loading of a case. A noticeable loss of primer pocket tension indicates that your ammunition has excessive pressure and has overworked the case."
As far as cratering goes, there are a lot of variables that contribute. In my case, I think I just have a bolt with a slightly larger FP aperture. It doesn't necessarily hurt anything but it's obvious the FP is too large. The 6CM, 6.5CM, 243Win, 260Rem, etc seem to be more sensitive to primer flow. This is not isolated to the AR10/AR308 platform either, bolt actions suffer from the same problem. Bushing bolt faces and turning firing pins has been going on for a long time.
This was copied from another site.
The term "high pressure" I think is just a way JP distinguishes their small diameter firing pin bolt from bolts with traditional size firing pins. If you read their site they list this warning:
"WARNING: The JP .308HP bolt does not allow for the use of excessive pressure, overloaded ammunition that exceeds SAAMI specifications. When evaluating new ammunition, always start on the low- to mid-range of any published load data and work up. A good indicator of working pressure is the primer retention on the subsequent loading of a case. A noticeable loss of primer pocket tension indicates that your ammunition has excessive pressure and has overworked the case."
As far as cratering goes, there are a lot of variables that contribute. In my case, I think I just have a bolt with a slightly larger FP aperture. It doesn't necessarily hurt anything but it's obvious the FP is too large. The 6CM, 6.5CM, 243Win, 260Rem, etc seem to be more sensitive to primer flow. This is not isolated to the AR10/AR308 platform either, bolt actions suffer from the same problem. Bushing bolt faces and turning firing pins has been going on for a long time.
Key phrase is “Hornady Superperformance“ this stuff always seems to be loaded to the ragged edge. I haven’t shot any of the 165 SST but all the other Hornady Superperformance I’ve shot over the years and most of the students I’ve seen running it all seems to have the same issues you’re describing. My advice is don’t bother with it especially for a gas gun.
Though it may be late now, but was it rainy or did you pull ammo out of a cold car? If the ammo had condensation or you had any moisture from rain on your brass or in the chamber it almost always goes way over pressure.
I could have sworn that Hornady had put out a public notice that Hornady Superperformance wasn’t meant for gas guns but that no longer appears to be the case. Either way I’m still not buying it, the real world performance seems to leave a lot to be desired.
Sorry we don't have much signal at the hunt camp. It is a Palmetto State Armory complete upper and lower run unsuppressed. It was about 50 degrees at home when I sighted in and about 85 in Florida when we went to verify our rifles. The ammo had been sitting out for most of the day under a covered porch on the cook shack. It went down in a plastic ammo can in the bed of a cap covered truck so it should not have been a drastic temperature change causing it. The Precision Hunter worked well. It ended up dropping 4 hogs in 1 day. I lost 1 the next day when it went into a flag pond after a solid hit.
This is the upper I have. I did swap out the muzzle device for an Area 419 Hellfire muzzle brake other than that I made no changes or modifications to the upper.
https://palmettostatearmory.com/psa...htweight-upper-with-bcg-and-ch-516447548.html
This is the lower. I did swap out the trigger for a James Madison Tactical saber trigger and added a Magpul Gen 3 PRS stock and MIAD grip.
https://palmettostatearmory.com/psa...08-lower-with-over-molded-grip-516446483.html
https://palmettostatearmory.com/psa...htweight-upper-with-bcg-and-ch-516447548.html
This is the lower. I did swap out the trigger for a James Madison Tactical saber trigger and added a Magpul Gen 3 PRS stock and MIAD grip.
https://palmettostatearmory.com/psa...08-lower-with-over-molded-grip-516446483.html
