AR 10 POPPING FACTORY AMMO PRIMERS

[Darryle]

Had the issue with 300 BLK. Had the time to compare sub to supersonic only using different brands. Not an apples to apples comparison by any means but in sub there were zero issues. Need to get another brand of super to confirm my gut feeling of bad primer size or pockets.

Factory assembled WW upper.

300 BO is low pressure compared to the 6/6.5 Creedmoor

 

[woodnut]

So, I had my 'smith run it and all he came up with was to use my reloads. I have since shot it and adjusted the gas block to just where it will hold open at last shot. Started with closed, got to operating but not holding open last shot. One more click did it.
But, I think I still need some range time with a chrono to see what my bolt gun loads are doing in the gas gun. I am not fully satisfied with the accuracy at 300. Could have been me, and or conditions, but others shooting it had no better results. But, at least I can shoot it now! I will also, just because, take some factory ammo and see if the new gas setting has helped. Fingers crossed! Will start the reloads with some seating deeper to see if that helps any. It's nit picking over accuracy, but hey, I want accurate rifles!

 

[Frog4aday]

I'm confused. Your gun was blowing the primers out of the factory loads which is why you posted to begin with. Now your gunsmith says everything is fine and you've adjusted the gas block to 'just' eject an empty case upon firing and...everything is fine? (Except accuracy.) I feel like I've missed something.

Your factory loads were making contact, upon chambering, with the rifling...or something, because you put black marker on the bullet and could see a distinct line of contact occurring. This seemed to be pointing to a short leade. Seating deeper with your reloads is fine (assuming you back off powder charge as needed to compensate), but doesn't address the fact that the Hornady "Black" factory ammo was blowing primers out in your gun.

Don't get me wrong - if YOU are happy - then...great! But I don't see how the underlying issue has been addressed/sorted out yet.

If it were me and my gun, now that your gunsmith has deemed the gun is "SAFE"(?), I would still want to address the problem is some way. I think DEL2LES was on the right track with what to try next:

I had a "match" 223 chambered barrel for an AR do exactly this very thing using factory 69gr match ammo, and it was due to a short leade and tight throat. Since the barrel was not lapped from the manufacturer, I fire-lapped it with a Tubbs kit, and after that, no more issues.

Perhaps give these a try.
http://www.davidtubb.com/final-finish-bullet-kits/finalfinish-bulletkit-243
I'm worried about your safety and the 'future' health of your gun. Something isn't right. Fire lapping can give your gun a bit of 'breathing' room in the leade area AND will likely help your accuracy issues, too. Could be the 'cheapest/best' $35 you spend at this point.

 

[woodnut]

Frog4aday, I completely agree with you! However, b4 I invest in 50 rounds of Tubbs ( as that's what I think they say to shoot), I want to spent some time on the range with my chrono and see what it tells me. Both with factory and reloads. I have seated some reloads deeper to see what effect it has in both my bolt rifle and AR. Yes, I know, that isn't addressing the factory ammo issue. Also, not addressing the throat issue either. But if my reloads, with tweaking, makes my AR accurate and safe, I will be content. I would be more content if the 'smith would rechamber it with a better reamer so I could use factory ammo. But I will take one step at a time. This barrel has had a few hundred rounds in it b4 it was re-chambered, so life is shorter than a new barrel. I don't hold a lot of hope that "tweaking" the reloads will solve the throat problem; but maybe it will allow me to safely and accurately shoot my reloads. The bolt rifles shoot factory (and reloads) very well so all is not lost. Will post my results when done. lately, rain and heat has been keeping me off the range so it may be a while b4 I get to go.

 

[Frog4aday]

Hey Woodnut,
Thanks for the response. It provides some clarity. You have a bolt gun you can fire your factory rounds through, so no loss there. And you reload, so you can tinker with COAL in the semi-auto to find a happy load for that gun, so it makes sense that you are just going to make do with things the way they are for now.

I do agree that it is frustrating that the gunsmith wouldn't tweak the chambering in the AR just a touch to lengthen the leade so the "Black" ammo would chamber without contacting the rifling. I think we've all been there - things aren't perfect or even the way we would ideally want them, but the issues are not fatal and there are work-arounds.

I hope you find a load your AR enjoys and perhaps it will work well in your bolt gun, too. Each will have an absolute favorite, but it is nice when you can find ONE load that works 'well enough' in multiple guns.

 

[Zymurgist]

Recently, I had an AR10 rechambered by a fine smith from 6x47Lapua to 6 Creedmoor. Went to test and zero it and two factory rounds had their primers blown out. Inspecting the primers showed no other pressure sign, but was black round it and the pocket was all black. Only two out of maybe 6 rounds. Other fired cases showed no pressure signs. Rifle operated normally.
I'm hoping ammo was at fault. It was Hornady Black, and I've never had anything like this to happen b4. But what do you think could have caused it?

I'd take the rifle and spent cases back to your smith and ask him/her.