Brass casing lodged in chamber. Extractor ring ripping off.

[Shooter14854]

I’m having a strange malfunction in my .308win AR10 I’ve never seen or experienced (been shooting the gun for years). The casing would get stuck so tight in the chamber the extractor on the bolt would rip the extractor ring off the brass case. I had to knock the casing out with a cleaning rod to remove the case. Even with the cleaning rod it still took a good amount of force to get the case removed. This happened twice in 50 rounds. Even the cases that did remove properly the extractor ring was bent slightly. I did not see any extractor wipe or any blown primers on any of the casings.
My question is, was this caused by the rifle being dirty or was my load to hot. I was using sierra 175gr hpbt with 48gr Win760 at 2.80 COL. The load shot great just had those strange malfunctions. I pulled the bolt and extractor on the rifle and it was pretty dirty but did not look physically damaged/bent. Thanks for the advice! Also, I havnt ever used that exact load before.

 

[JohnKSa]

When you were working up to that powder charge did you have any problems with extraction with the lighter powder charges?

 

[Shooter14854]

When you were working up to that powder charge did you have any problems with extraction with the lighter powder charges?

No I didn’t ever. Last load out was at 47gr

 

[bangswitch]

How many times have you loaded those cases? Are they standard .308 or NATO 7.62x51? Sound like case head separations from too many uses. AR's and other military style rifles (M1 Garand and M1A) are notoriously hard on brass, and most cases won't handle more than 4-5 reloadings before cracking or separating at the case head, Make yourself a tool using a paperclip straightened out, with a tiny hook on one end. When processing your brass, run the hooked end down to the case web and start moving it up and down inside against the case wall. You'll be able to feel where the case thins just above the web, and may even snag on incipient cracks that haven't worked through the brass yet. Any questionable cases, pitch them. I can't question your loads, but if you've been using that load for a while and don't see pressure signs, I guess you're good to go.

I load for an M1A, and never go more than 4 reloads on once-fired brass that I buy. I use Lake City NATO brass exclusively in my rifle, and I check them after every firing like I described above.

 

[hso]

Too much energy. You're ripping the cases apart. You're also probably damaging your lugs.

I had that with an FAL that needed to be adjusted to reduce the gas driving the cycle.

 

[d2wing]

I don't know if this applies to an AR-10 but I needed a heavier buffer to slow action with an AR with that problem.

 

[Ironicaintit]

If this is a new phenomenon; what changed? Is this a new load, or the same one you have been using?

I'd look pretty close at the chamber for burrs or just accumulated gunk.

 

[trackskippy]

You may want to check your books again. All three of my manuals show a tic over 48 grains of 760 with that bullet being a max load. Those cases sticking and ripping the rims out, sounds like it might could be pressure to me. What did the primers look like?

 

[bangswitch]

I wonder if the dry case lube would work, like the spray stuff Hornady makes. I'll give it a try, nothing ventured, etc.

 

[earplug]

I think your over gassed. Ripping a rim off is not a failed case issue. From the information given and from what I have read your powder is not good for a gas gun in .308 Winchester. If your stuck with a lot of the powder a adjustable gas block might be your solution.

 

[Fooey]

How many times have you loaded those cases? Are they standard .308 or NATO 7.62x51? Sound like case head separations from too many uses. AR's and other military style rifles (M1 Garand and M1A) are notoriously hard on brass, and most cases won't handle more than 4-5 reloadings before cracking or separating at the case head, Make yourself a tool using a paperclip straightened out, with a tiny hook on one end. When processing your brass, run the hooked end down to the case web and start moving it up and down inside against the case wall. You'll be able to feel where the case thins just above the web, and may even snag on incipient cracks that haven't worked through the brass yet. Any questionable cases, pitch them. I can't question your loads, but if you've been using that load for a while and don't see pressure signs, I guess you're good to go.

I load for an M1A, and never go more than 4 reloads on once-fired brass that I buy. I use Lake City NATO brass exclusively in my rifle, and I check them after every firing like I described above.

He is ripping off the part the extractor grabs, not the whole case head. so I don't think it is case head separation. Sounds to me like some hot loaded ammo. Case is sticking in chamber is a clue. Try some other factory loads to see how that does the same or works OK. Or maybe take apart some of the ammo and weigh the powder charge. See if it looks like the right powder. In any case I would not fire anymore of these without investigation Shooter.

 

[Robert]

Let's focus on the OPs question and stop chasing rabbits...

 

[jmorris]

I’m having a strange malfunction in my .308win AR10 I’ve never seen or experienced (been shooting the gun for years).

What is the variable (change) that made the rifle change from zero malfunctions over years to destroying two cases in 50 rounds?

First thing I would do, is to change that one back and see if everything is OK again.

 

[GooseGestapo]

Removed by poster

 

[lysanderxiii]

Winchester 760 is too slow a propellant for an AR 308.

This is giving you excessively high port pressures and excessive bolt velocities.

Switch to a faster propellant,

 

[someguy2800]

Ripping the rims off can mean that the gas impulse inside the bolt carrier is too high pressure or just happening too early while the case is still stuck to the chamber walls by residual chamber pressure, but in this case since you said the spent cases are hard to remove with a cleaning rod I would say this is simply and overload in this specific gun.

temperature is also a big factor, an otherwise safe load can suddenly become overpressure in hot weather.

 

[someguy2800]

When the book says a load is safe but the rifle says differently, listen to the rifle

 

[MachIVshooter]

Sticky extraction/cases getting stuck in chambers is either rough chamber or overpressure load. Since you've had no problems previously, can pretty well rule out chamber finish.

With a gas operated autoloader, the overpressure condition that causes case sticking is compounded with higher port pressure making the gun cycle faster, attempting extraction a little bit earlier.

 

[RainDodger]

Someone in this thread said, "I wonder if the dry case lube would work, like the spray stuff Hornady makes. I'll give it a try, nothing ventured, etc."

Maybe I read that incorrectly, but it sounds like you're going to lube a case before firing it. Don't do that. Solve the problem the right way first.

 

[Dave DeLaurant]

Do you have access to a bore scope? A burr or nick inside the chamber is a distant possibility.

I bought a Swiss 1889 rifle last year with a torn, thoroughly stuck case jammed into the chamber -- once I got it out I found a burr in the chamber near the shoulder.

 

[N555]

Tell us more about your rifle?
Carbine or rifle length?
Silencer?

I have had trouble with carbine length gas systems running max loads of w760 and roughly w760 speed powders ejecting cases into the next county and causing harsh recoil, from rearward motion of the bolt.
No stuck cases like that, maybe I just got lucky.

Rifle length guns didn't seem to have a problem at all with this load and ran it great, even with a silencer.

 

[N555]

Winchester 760 is too slow a propellant for an AR 308.

This is giving you excessively high port pressures and excessive bolt velocities.

Switch to a faster propellant,

Yes for carbines I like H322 to W748/BLC-2 speed powders.

 

[N555]

I don't know if this applies to an AR-10 but I needed a heavier buffer to slow action with an AR with that problem.

Yeah you can get a steel body buffer and put tungsten weights in it at least for an AR10 carbine. But it sounds like this ammo is too hot or the gun way over gassed, more than what a heavy buffer can fix.

 

[bfoosh006]

As mentioned WC760 is to slow of a burning propellant for the direct gas impingement action of your Large Frame AR. Especially at your charge weight.

Your gas port pressure level is exceeding your rifles action "specs" . IE It is trying to vigorously extract at high pressure levels... from both the chamber pressure level and the gas port pressure level / cyclic speed.

BACK your load off. Or use a better suited burn rate powder ( IMR 4895, IMR 4064 and quite a few newer ones )

I realize powder is hard to come by... but ...

I didn't see you gas length system ( Rifle ? , Middie ? .. Carbine ? ) Hopefully you have a rifle length gas system... a Carbine length could have be a more serious issue.

Also.. you didn't mention what brand brass you are using. Mil-Spec 308 / 7.62x51 brass has less internal volume then "most" commercial 308 brass.. and that can cause serious pressure increases at your charge weight mentioned.

While you "might" be able to restrict the gas port volume "enough" with an Adj. GB... I still wouldn't try it.

As for trying to adjust via buffer weights / recoil springs... I still wouldn't suggest it with that slow of a burning powder.

 

[Nature Boy]

As mentioned WC760 is to slow of a burning propellant for the direct gas impingement action of your Large Frame AR. Especially at your charge weight.

Winchester 760 is too slow a propellant for an AR 308

I’m with these guys. Wrong powder choice and too much of it for a gas operated rifle.