Fired Brass Can't be Re-Sized

[cohunt]

Yes, as far as I can tell the brass does re-chamber after firing. But, how can I be sure that the bolt is closing and rotating all the way on a semi auto?

does the hammer cock and then fall when you pull the trigger? if the bolt inst closed all the way, you shouldnt hear the hammer fall

other way to be sure, would be to open the upper/lower and try to close the bolt with your thumb on a piece of fired brass, you should be able to see/tell when the bolt is closed and the carrier is all the way forward as it would be clear of the upper so the lower will close and not hit the carrier

 

[woolecox]

does the hammer cock and then fall when you pull the trigger? if the bolt inst closed all the way, you wont hear the hammer fall

other way to be sure, would be to open the upper/lower and try to close the bolt with your thumb on a piece of fired brass, you should be able to see/tell when the bolt is closed and the carrier is all the way forward as it would be clear of the upper so the lower will close and not hit the carrier

Thanks, I will try all that when I get home.

 

[greenejc]

I just got a factory new AR10 chambered in 7.62 NATO (308Win). My first 7.62 auto loader. I am a reloader. I have been doing it for 30 years now. I have been an active Bench Rest, PRS, and IDPA competitor and, reload for all those disciplines. I also reload all my hunting ammo. So, I am pretty sure I know what I am doing and am confident my equipment is up to and exceeds par.

Using a box of new Lapua 308 Win brass I had on hand, I loaded up several "ladders" that consisted of 168SMK, 175SMK, 175VLD-H, and 178ELD-X. All respectable bullets. All were loaded using various weights of Varget power, and GM210M primers. All top shelf components. None of the loads were anywhere near max. In most, at least two full grains short. No over pressure signs.

I also shot a couple of factory loads, Hornady Black 168AMAX, and Federal Gold Medal Match. All reloads and factory ammo functioned flawlessly except the factory Fed GMM. It was not powerful enough to strip the next round from the magazine and closed on an empty chamber. "CLICK". The GMM did function flawlessly with the gun suppressed but the groups were terrible. All other groups were near or under 1 MOA for 5 shots. The best was the 178ELD-X that grouped .62" and clocked 2500 fps. It's a 20" barrel.

To the point: All cases except for the Hornady case will not go through my resizing dies. Even with the Hornady I really had to stand on the lever to get them sized. When I measured the fired cases, all dimensions were around a full .01" larger than factory new. A full hundredth. No way they are going through a die. Yes, I used multiple dies; Redding FL, Redding Type S, Redding Shoulder Bump, Forster FL, and Forster Bushing Bump. Not happening.

So the question: Can this be anything other than an extremely loose chamber?

I am going to contact the factory as soon as possible but, that may be impossible with most companies being flat on their butt "due to COVID".

Here is one of the better groups. The factory Hornady AMAX did just as well.
View attachment 205436

As a suggestion, you might try some military brass, but it is almost certainly a loose chamber. You may need to get one of your dies reamed for that rifle by a good gunsmith. A lot of the milspec ARs have chambers that are less than tight so they can chamber and fire anybody's 7.62 Nato, some of which is not as well made and high tolerance as ours is. If they will correct the problem, ask for a match chamber in your new barrel.

 

[greenejc]

https://www.hornady.com/support/superformance-in-gas-operated-firearms

Suppressed-
??

Hornaday is right about firing with a suppressor on the rifle. It ups the pressure and you're already extracting the casing while under pressure in a semi-auto firearm. As the casing is pulled from the barrel, the suppressor only increases the pressure while it is essentially unsupported. What do the casings look like when you don't use the suppressor?

 

[Huntz]

If you read the saami print-- down near the bottom right under the chamber dimensions--- there is a notation that says " CHAMBER" and it is underlined--- it says "unless otherwise noted all dia +.002" (.050mm)" and then it says "length tol. +.015" (0.38mm)" so you have a +.002" diameter and +.015" length tolerances over what the drawing specifications state.

Is it a 308W chamber, or 7.62x51 nato? I dont know where to find Nato spec drawings, but I'm pretty sure that the nato chambers are looser


so your chamber has a max diameter of .002" larger than the chamber print (so .4734" at base and .4571" at shoulder--diameter) and a max length of +.015"
you will also note that the "datum line" measurement does have a min and max-- this would be 1.630" min and 1.604" max --these would be your head space measurements


just found that nato max is 1.6455 for headspace, not sure on diameter yet


you said your brass was oversize--did I miss where you said if it was over length or over diameter?

as far as the rifle manufacture, I hope they stand behind it if the chamber is out of spec, BUT most manufactures will plainly state in the manual that if you shoot reloaded ammo in your rifle it will void the warranty, so you may be opening up a can of worms by telling them you are trying to resize the brass to reload

Almost all firearm manufacturers have a caveat written in their Operators manual that firing reloaded ammo voids their warranty.

 

[ScottB338]

Yes, as far as I can tell the brass does re-chamber after firing. But, how can I be sure that the bolt is closing and rotating all the way on a semi auto?

You could also just punch out the primer and seat a live one. That would tell you for sure that you have adequate bolt lockup.

 

[243winxb]

To add more fuel to the fire

SAAMI doesn't list any problems SAAMI link

 

[lyle2231]

AR's brass needs to be fully resized else you'll be running a rod down the muzzle. If I was in your shoes I'd call the manufacturer with an ammo question "Can I run reloads " Will it void my warranty? Going by what they say...then call again with the over sized brass question. Secondly look on the net for AR smith.
I would suggest White Oak Armament. John doesn't work on '10s anymore but he is very knowledgeable. HTH

 

[DCAN]

I've had a number of gas guns over the years. Best guess is you were blessed with a generously sized chamber. Greenejc hit the nail on the head. Nato chambers are not the same as a Wylde or match chamber. If we were talking about a bolt gun, this situation would be unacceptable, at least for me. Since we are dealing with a gas gun, which seems to shoot really well, I'd have a custom die made and call it a day. Having an accurate AR10 which will except just about any kind of 308 ammo you want to stuff in the mag? Bonus! Seriously, I've had overly tight chambers opened up in my AR's over the years. Made life way easier and they never lost a hint of accuracy.
You no doubt know this, but, just in case, don't expect long brass life from a gas gun. My M1A is not kind to it's brass. Max is 4 reloadings, and that's with mil spec brass. My AR's are better, but still nothing like a bolt gun. Best of luck with the new smoke pole!

 

[Eric Alexander]

A custom die may be the answer or, a new barrel with a proper chamber or, leave the brass laying on the ground.

I will let you know what the factory says if I can get a hold of a human.

I think you had it correctly assessed with your first comment on outsized chamber. So, then if they send you a standard off the shelf barrel, it may be more of same. Perhaps you get them to send you an unchambered barrel and you get it chsmbered. I don't necessarily think that soution is equitable, and you aren't getting paid to work for them, but it may be a workable compromise.... short of a refund.
Hope this story turns out ok for you.

 

[Wild_Bill]

Hi i need to chime in,
.010" case expansion is DANGEROUS. Do not try to reload any of that brass you WILL get case head separations.
Could you measure one of the cases you fired that did not cycle the action correctly. It should have the smallest expansion as it should be the lowest pressure.

People have stated you must use small bases dies in autoloader that is not correct and in this case it would be worse.
To the guy that heats his cases with a blow touch please stop that as you are annealing the case head and will kill someone.


The chamber is either way to large or the bolt is unlocking prematurely.
A chamber case as mentioned will clarify if the chamber is oversized, it might also have an extra strong main spring . Can you re chamber a fired case? If you can the chamber is definatly oversize. If not it would need casting as it might be a timing issue.

I used to load for AR15, AR10, SLR, M14,M1 Carbine, M1A, SKS, FAL, Valmet Hunter 308, Hakim 8mm. I never used a small base die for any of them and the brass was not .002" larger in the base after firing.

I hope the company stands by there product.

Good luck Bill

 

[cajun]

So what is the actual measurement of your fired brass at the web just above the extractor groove and at the neck shoulder junction? This measurement is best taken with a micrometer but a caliper will suffice.

 

[woolecox]

Hi i need to chime in,
.010" case expansion is DANGEROUS. Do not try to reload any of that brass you WILL get case head separations.
Could you measure one of the cases you fired that did not cycle the action correctly. It should have the smallest expansion as it should be the lowest pressure.

People have stated you must use small bases dies in autoloader that is not correct and in this case it would be worse.
To the guy that heats his cases with a blow touch please stop that as you are annealing the case head and will kill someone.


The chamber is either way to large or the bolt is unlocking prematurely.
A chamber case as mentioned will clarify if the chamber is oversized, it might also have an extra strong main spring . Can you re chamber a fired case? If you can the chamber is definatly oversize. If not it would need casting as it might be a timing issue.

I used to load for AR15, AR10, SLR, M14,M1 Carbine, M1A, SKS, FAL, Valmet Hunter 308, Hakim 8mm. I never used a small base die for any of them and the brass was not .002" larger in the base after firing.

I hope the company stands by there product.

Good luck Bill

Very good advice. No way I would reload that brass, even if I could.

 

[JayCee49]

Hello, just found this in www.shootingillustrated.com https://bit.ly/3ghLDms :

"First of all, the headspacing on most 7.62 NATO chambers will run 0.006 to 0.010 inch longer than their sporting rifle counterparts, to allow for proper feeding and ejection during repeated, rapid firing. Combine a longer chamber with a thinner case—the .308 Winchester cases will be thinner than military 7.62 NATO cases—and you open the door for the possibility of a ruptured case. A good rule of thumb is that a .308 Win. chamber can handle both types of ammunition, but a 7.62 NATO chamber should only fire 7.62 NATO ammunition. This avoids any potential problems in a chamber with intentionally excessive headspacing.

Secondly, for those that reload their own ammunition, it is imperative that you sort your cases, segregating any cases with the 7.62 NATO headstamp, as the load recipes which have been proven safe in the thinner case (having a larger combustion chamber) will generate higher pressures in a more confined space.

The actual pressure differences between aren't all that large—a 62,000 psi limit for the .308 Win. and 60,200 psi for the 7.62 NATO—but it's enough to be concerned with; a tight chamber, or an overly dirty chamber could pose a pressure issue. No one wants to damage a firearm, and we certainly don't ever want to see anyone hurt; so keep the golden rule in mind: a .308 Win. chamber can handle both .308 Win. and 7.62 NATO ammo safely, but if your rifle is marked for 7.62 NATO ammo, it's best to use only that."

Maybe this is a preview of what the manufacturer will say?

JMTC,

JC