Case mouth ring separation

Moderators: gds, bakerjw, renegade, bamachem

User avatar
dellet
Silent But Deadly
Posts: 5836
Joined: Fri Nov 30, 2012 1:25 pm

Re: Case mouth ring separation

Post by dellet » Sat Apr 13, 2019 11:35 pm

Some people special order a tight bore. :mrgreen:

It might be easier to measure the bullet if there is enough there.

If you have a cast bullet it would be easier to drive through. If not I would try a cleaning jag and tight patch.

I looked back at your original post and it was a bit confusing. If I read it right this is a Spikes tactical 10.5” barrel that has about sixty rounds of factory Hornady subs, then 25 of your reloads.

Were the reloads from the original Hornady ammo?

The barrel will not be made by AAC, unless it was cut down. They never made a 10.5”. It may be marked with the full SAAMI name “300 AAC Blackout”.

Did you try that bullet twice? Wondering about the markings
300 Blackout, not just for sub-sonics.

BulletFlight for Android
Okiedelta
Member
Posts: 26
Joined: Sat Mar 30, 2019 2:41 pm

Re: Case mouth ring separation

Post by Okiedelta » Sun Apr 14, 2019 12:13 am

Yes. I tried twice on the bullet. That’s why one set of the land marks is shorter.
The barrel is Spikes Tactical, and the stamp on the barrel is 300 AAC.

The reloads weren’t from the factory used cases, they were cut down and resized used 5.56 brass from LC.

I’ve tried a jag with tight patches, but not a cast bullet. I’ll give that a try tomorrow.

Thanks for your patience.

User avatar
brutis
Member
Posts: 35
Joined: Mon Jul 11, 2016 6:19 am
Location: Nebraska

Re: Case mouth ring separation

Post by brutis » Sun Apr 14, 2019 7:01 am

When you stick an unloaded case in the chamber, by hand, how much of the case sticks out? Should be around .128". This would tell us how long the obstruction is in the chamber.

Have you tried an 7.62 broken case extractor?

A Midway USA video

Okiedelta
Member
Posts: 26
Joined: Sat Mar 30, 2019 2:41 pm

Re: Case mouth ring separation

Post by Okiedelta » Sun Apr 14, 2019 9:13 am

It’s difficult to measure how much sticks out, but it sure looks like more than 1/8 inch.

I don’t have a 7.62 broken case extractor. I do have an original M1 Garand combo tool with a very stiff copper brush. I know the tool also has a case extraction function but I haven’t used it for that. I’ll try that out today.

My other plan is to wrap a jag with a couple of patches for a tight fit and run it in from the muzzle end.

When I started this thread, I was really looking for an explanation why this kind of case mouth separation happened. I thought the extraction would be simple.

User avatar
dellet
Silent But Deadly
Posts: 5836
Joined: Fri Nov 30, 2012 1:25 pm

Re: Case mouth ring separation

Post by dellet » Sun Apr 14, 2019 10:22 am

Explaining how it happened will be difficult until you know for sure what the ring is. If it’s a single case neck the last round fired should have been measurably shorter. If it’s a bunch of rings stacked it might be a completely different cause. If it ends up being jacket material, something else.

Once it’s out, a chamber cast might be a good first step.

Comparing fired dimensions of the two different brands of brass might also give a clue.
300 Blackout, not just for sub-sonics.

User avatar
wildfowler
Silent But Deadly
Posts: 641
Joined: Sun Mar 30, 2008 8:40 am
Location: Mis'sippi

Re: Case mouth ring separation

Post by wildfowler » Mon Apr 15, 2019 2:47 am

Okiedelta wrote:
Sun Apr 14, 2019 9:13 am
When I started this thread, I was really looking for an explanation why this kind of case mouth separation happened. I thought the extraction would be simple.
No help on the removal from me.

I have a wildcat 30 cal I use in an AR that does this with a little regularity. It takes several re-loadings on an individual piece of brass. Those pieces that I don’t toss due to primer pockets being too loose tend to fail at the shoulder for me for some reason in this caliber. My case failure is where the case neck meets the case body, so the broken piece includes the shoulder. And what’s left of ejected case looks like straight wall pistol case without the rim.

My problem is that I rarely notice a crack in the brass ahead of time and wind up firing the round. Jamming the next round out of battery like you described.

I guess I’m fortunate because the way the broken piece of brass is broken off it either drops out on its own or is pulled out when removing the live round that didn’t go into battery. I’ve always been able to clear the obstruction in the field.

This wildcat caliber “resembles” a 300 blkout case with a relatively short neck, but is based on the 6.8 case. This makes me wonder if I’ve been measuring my shoulder bump incorrectly and over sizing the case.

I have tried to verify my measuring procedure and feel like my numbers are correct. But I am convinced there is something in my reloading process that is causing this case failure and I am convinced it’s related to how I size the case.

I would estimate that I’ve seen this 10 times out of approx 2000 rounds fired. But remember, I am talking about a cartridge that is NOT a 300 blackout.
driven every kind of rig that's ever been made, driven the backroads so I wouldn't get weighed. - Lowell George

cdl
Silent Operator
Posts: 63
Joined: Thu Sep 15, 2016 2:30 am

Re: Case mouth ring separation

Post by cdl » Mon Apr 15, 2019 3:29 pm

I have a carton of Spanish 7mm Mauser from 1920 that will do that pretty much on demand... and it's "Brand new old stock".

I also have a bag of old HK91 & Cetme fired 308 brass that I've reloaded to death and save for the same. They look good, in a barber pole kind of way, but same thing, neck and shoulder separations.

I blame it mostly on brittle brass. There can be a lot of contributing factors I'm sure, but brittle brass seems a common denominator for me.

Since I have this history, I anneal all my new 300 Blk. Actually I kind of expected it with 300 Blk. But I have never seen it in my 300 Blk. A few cracked necks, but it seems the primers start falling out first. But 300 Blk gets worked pretty hard when it's made. And who really knows the history of the range brass it came from. And if you only have a few, they can get recycled many times. And if you FL resize with small base dies they get worked even more.

In my experience, the notable event was the next round not cambering. Nothing earth shattering. I could explain how I use to use a folded chunk of coat hanger with opposing barbs bent in the ends but it's not something you want people to know you did. I carry stuck case removers now. With 300 Blk and a short barrel, I'd probably tap the 762 version out from the muzzle with a rod, but carefully, because you could really jamb it up. So I probably wouldn't want people to know that either...

Something to think about anyway.

Okiedelta
Member
Posts: 26
Joined: Sat Mar 30, 2019 2:41 pm

Re: Case mouth ring separation

Post by Okiedelta » Mon Apr 15, 2019 11:22 pm

I waiting on a chunk of Cerrosafe to get here so I can get a chamber cast and hopefully pull the brass part out with it.

I’m starting to think maybe this was a slow collection of brass ‘dust’. The first 40 or so commercial rounds through the new barrel a few weeks before left a lot of brass shavings in the lugs and on the bolt face. So I had pulled the barrel and polished the feed ramps and smoothed out some sharp edges.

That was all before the current problem. Wondering if every time a shell was ejected some shavings got into the chamber and were just packed down every time a round chambered, eventually building up enough brass that it stopped the last round.

User avatar
dellet
Silent But Deadly
Posts: 5836
Joined: Fri Nov 30, 2012 1:25 pm

Re: Case mouth ring separation

Post by dellet » Tue Apr 16, 2019 12:27 am

Have you tried to chamber an empty case?

I would be inclined to try a couple things. If an empty case will not chamber, I would trim maybe .005” and try again until the bolt closes. A stripped bolt would be best. This will give an idea of how much brass is in there.

If it closes on an empty, then you know it’s farther forward and hanging up on the bulllet. Then I would compare the length the bullet used to hit the lands at and how much shorter it is now.

With that information it might change my next step, that may or may not be suitable to print on an open forum :shock:
300 Blackout, not just for sub-sonics.

Okiedelta
Member
Posts: 26
Joined: Sat Mar 30, 2019 2:41 pm

Re: Case mouth ring separation

Post by Okiedelta » Tue Apr 16, 2019 3:48 pm

I’ll run those options tonight.
Thanks for bearing through this with me.

Post Reply