260 Rem popping primers on factory ammo

[jwfuhrman]

I'm hooked into 260 Remington pretty deep, bought into that caliber before 6.5 came out and I have so much brass AND a ton of factory loaded Gold Metal Match and Hornady ELD-M ammo for it that is why I use it.

That being said, here's whats going on and I want to kinda run it passed the forum here to make sure I'm going in the right direction of thinking or if I'm WAYYYYYY out in left field.

Les begin the trouble shooting below shall we.....
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I purchased a Saturn Barrels 18in 260 Remington barrel with rifle length gas. At first I was having nothing but stove pipe/double feeds. Got an adjustable gas block and a DPMB Dual Extractor Bolt and that solved the issue of that. Damn gun runs at 7 clicks open unsuppressed and 1 click open suppressed on the gas block. I had this issue on all the platforms I've tried this barrel on so I'm pretty sure the barrel is way over gassed hence the adjustable gas block. I started noticing, especially when suppressed, that after about 10-15 rounds, when the rifle really starts to heat up, I'm literally popping every primer on every shot.

Am I correct in thinking that this chamber is undersized an as the rifle builds up heat is causing massive pressure issues? All I have been shooting is factory loaded ammo that I got pre-insanity pricing via RSR Group and Davidsons, I got a couple thousand rounds of each. This issue happens with both the Federal Gold Medal Match 142gr ammo and Hornady 130gr ELD ammo.

I need to get a Go/No Go gauge and a chamber reamer. Anyone know where I can find those?

Just some info on the rifle itself. It is a DB10 that runs 100% with 308 barrel. I have 2 others in 308 that run absolutely amazing (granted, those both have the barrels replaced with Ballistic Advantage barrels and DPMS Dual Extractor Bolts) I've tested this 260 barrel on multiple other AR10 platforms with same results.

[Failure2Stop]

Define "popping primer".

[markm]

You have any chrono data to help dial this in at all?

[jwfuhrman]

Blowing primers completely out of primer pocket. I have not chrono’d any of this ammo, probably should!

Will say that, while it’s a bolt action, when shooting this ammo thru my Savage 110 Predator in 260 REM, it does not show any pressure signs at all.

[markm]

Will say that, while it’s a bolt action, when shooting this ammo thru my Savage 110 Predator in 260 REM, it does not show any pressure signs at all.

Definitely pointing to a chamber or bore issue. Do you have a riflesmith who could pin gauge the bore? That'd be the cheapest and easiest starting point.

[jwfuhrman]

I do indeed. That’s the way I was leaning I just wanted to kinda throw the issue and question out there for you guys. Wanted to make sure I was thinking correctly on what was causing the issue.

With that said, anyone got barrel recommendations? It’s an 18in barrel and I’m debating on going up to a 20. Still shorter than the 24in on the bolt gun, but longer to get the extra velocity.

Jack I think I just saw you post in a thread about short 6.5’s and 16 and 18 guns for that were performing wonderfully, but 260 is just different enough that I’m not sure a little longer isn’t better barrel wise.

[Todd.K]

I think that “dropped primer” is a better term.

I have seen it from several calibers in the AR-10. I believe it may be ammo related, as certain lots would see this problem while others would not.

My theory:
The AR-10 may not support the cartridge base as much as ideal, allowing the base to expand under pressure. It then may extract too early and eject too violently. So if the brass is a bit softer, or the primer pocket is a bit larger, it all adds up to not hang onto the primer when the case is ejected.

Some problem with the chamber raising pressure would also increase some of the problems above.

[constructor]

I'm hooked into 260 Remington pretty deep, bought into that caliber before 6.5 came out and I have so much brass AND a ton of factory loaded Gold Metal Match and Hornady ELD-M ammo for it that is why I use it.

That being said, here's whats going on and I want to kinda run it passed the forum here to make sure I'm going in the right direction of thinking or if I'm WAYYYYYY out in left field.

Les begin the trouble shooting below shall we.....
------------------------


I purchased a Saturn Barrels 18in 260 Remington barrel with rifle length gas. At first I was having nothing but stove pipe/double feeds. Got an adjustable gas block and a DPMB Dual Extractor Bolt and that solved the issue of that. Damn gun runs at 7 clicks open unsuppressed and 1 click open suppressed on the gas block. I had this issue on all the platforms I've tried this barrel on so I'm pretty sure the barrel is way over gassed hence the adjustable gas block. I started noticing, especially when suppressed, that after about 10-15 rounds, when the rifle really starts to heat up, I'm literally popping every primer on every shot.

Am I correct in thinking that this chamber is undersized an as the rifle builds up heat is causing massive pressure issues? All I have been shooting is factory loaded ammo that I got pre-insanity pricing via RSR Group and Davidsons, I got a couple thousand rounds of each. This issue happens with both the Federal Gold Medal Match 142gr ammo and Hornady 130gr ELD ammo.

I need to get a Go/No Go gauge and a chamber reamer. Anyone know where I can find those?

Just some info on the rifle itself. It is a DB10 that runs 100% with 308 barrel. I have 2 others in 308 that run absolutely amazing (granted, those both have the barrels replaced with Ballistic Advantage barrels and DPMS Dual Extractor Bolts) I've tested this 260 barrel on multiple other AR10 platforms with same results.

Brownells or midway for gauges(243,260,308) all the same they may have reamers also. Blown primers can be a sign of excess headspace.

[rainman]

Brownells or midway for gauges(243,260,308) all the same they may have reamers also. Blown primers can be a sign of excess headspace.

Constructor, this seems almost counterintuitive to me; I would have thought it would be the other way around. Apparently I don't understand headspace (other than knowing it's important). I'd appreciate a short explanation on this if you have the time.

Thanks in advance.


-Rainman

[constructor]

Constructor, this seems almost counterintuitive to me; I would have thought it would be the other way around. Apparently I don't understand headspace (other than knowing it's important). I'd appreciate a short explanation on this if you have the time.

Thanks in advance.


-Rainman

Extra length in the chamber means there is nothing to back up the primer, it blows out the rear.