Fired Brass Can't be Re-Sized

[woolecox]

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.

 

[Beluebow]

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

Yup, could be you got a fat chamber.

 

[woolecox]

Yup, could be you got a fat chamber.

I can probably write the company's response;

"We did not build this rifle for reloaders. We built it for war fighters so it would function with any ammo under any conditions. And, that is exactly what it does."

Hope I'm wrong.

 

[Dean2]

Have you compared the fired case measurements to the SAAMI specs. It sounds like you would be quite a ways over Spec if you can't get them to go through a sizing die. I don't care what the company built the rifle for, it still needs to conform or their needs to be a warning to the buyer prior to purchase.

308 is page 122. If you put that in the page count right at the top of the screen and hit enter it will save you scrolling through 121 pages.

https://saami.org/wp-content/uploads/2019/02/ANSI-SAAMI-Z299.4-CFR-Approved-2015-12-14-Posting-Copy.pdf

 

[woolecox]

Have you compared the fired case measurements to the SAAMI specs. It sounds like you would be quite a ways over Spec if you can't get them to go through a sizing die. I don't care what the company built the rifle for, it still needs to conform or their needs to be a warning to the buyer prior to purchase.

Yes, I have and the fired cases are about one hundredth of and inch (10 thousandths) over SAAMI or any factory ammo I have. They are just too blown out to resize.

I agree. I would likely not have bought this rifle if I knew it would ruin brass. But, I am not going to beat them up too bad until they have a chance to respond.

 

[243winxb]

All cases except for the Hornady case will not go through my resizing

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

Suppressed-

Hornady- the gun is still in the process or firing while it's trying to extract the cartridge case

??

 

[243winxb]

factory Fed GMM. It was not powerful enough to strip the next round from the magazine and closed on an empty chamber. "CLICK".

High pressure may make brass stick in the chamber on firing. Delayed extraction. Look for rim damage from the extractor.

But it worked suppressed, so port pressure was low when not suppressed.
May need an adjustable gas block?

 

[tigguy]

Need to run them through a small base die? Maybe that'd help but I'm not positive

 

[Dean2]

The issue is he can't get the case to go into the sizing die at all. The cases have over expanded so much they exceed the interior dimensions of any sizing die. Small base would be even worse.

 

[cajun]

You can do a chamber cast to see if its out of spec.

 

[Mikecr]

His brass IS the cast, and the test. It's a Lousy chamber

 

[Dean2]

You can do a chamber cast to see if its out of spec.

The ejected case size is a chamber cast, and they are .0005 or so under the actual chamber size due to the springiness of brass. However, the stuff a couple of guys posted about gas guns trying to eject the brass too soon may have applicability to the cases coming out so much over size. Be interesting to shut off the gas port and see what the brass measures after firing them single shot.

 

[tigguy]

The issue is he can't get the case to go into the sizing die at all. The cases have over expanded so much they exceed the interior dimensions of any sizing die. Small base would be even worse.

 

[cajun]

Yes but with a supressor and being a semi auto you have 2 additional variables. A chamber cast would eliminate those other variables. Fwiw most AR10's really need an adjustable gas block. It hard to get multiple loads to cycle properly without one.