5.56 LC Brass Case Failure?

[sawgunner2001]

Load data:
3x fired
23.5gr Varget
75gr BTHP
2.255” COAL
2650fps
Rifle: 20” RRA AR-15

When I was working up the load, I went as high as 24.2gr, without seeing any ejector swipe or primer issues.

I should add that the brass was purchased as once-fired from a reputable vendor. The other two firings were in my rifle.

I should note that these were FL resized after each firing. For the longest time, I set up my die to bottom out on the shellholder for a maximum resize because:
A.) I didn't have a comparator tool
B.) They were being used in an AR, and wanted a full, FL size for reliability

At some point, I bought a comparator tool and checked the measurements of fired cases and my sized cases and noted that I was sizing my cases far too much, even for reliability in an AR. I don't have the actual measurements handy, but I'd be willing to bet that the two sizings these cases experienced were too much.

These are my first case failures. I don’t have anymore loaded ammunition out of this lot of brass, but I’ve got about 500pcs of twice fired that’s ready to load (they're in two buckets - one marked "oversized" and one marked "sized correctly" - but the "sized correctly" bucket would have been oversized between the first and second firing). Are those safe to load?

Lastly, I would have expected the case failure closer to the base of the case…are these failures in a typical location, or is this indicative of a different problem?

 

[Txhillbilly]

What is the date headstamps on the brass? I bought a bunch of virgin LC brass several years ago from Natchez with 2009, 2010, and 2011 headstamps, and there are a lot of them that split necks the first firing out of several of my 223 / 5.56 AR's and bolt actions.
I think the brass was probably rejected by LC, and then sold on the consumer market by outfits like Natchez. I've never had this issue with any other LC brass with headstamp dates older or newer.

 

[37L1]

You oversized both batches so expect the same results if you reload and fire them. Best to start over with different brass and resize correctly. It's not fun to have one totally fail and then have to get the pieces out of your weapon. Don't mess around with things that can go wrong.

I'm sure you knew this but wanted to hear it from someone else.

 

[whatsupdoc]

The location of the crack is odd, bottoming the die to the shellholder would
reduce brass life but usually the case head would seperate just above the case web.

I would not use it as it may cause flame cutting of the chamber.

 

[sinister]

You'll have to hand-check each case for incipient case separation. You've probably trashed the entire lot.

You only need to re-size .002 inches for best feeding and reasonable case life.

 

[slowworm]

The location of the crack is odd, bottoming the die to the shellholder would
reduce brass life but usually the case head would seperate just above the case web.

I would not use it as it may cause flame cutting of the chamber.

Agreed. I've never in 20 years had a case split in the middle, and I FL resize to the shell holder all of my gas gun ammo. Neck splits, yes, and head separations where you say, but never in the middle. I have to wonder if the brass was polished with something known to attack brass, like an ammonia based polish.

Something is wrong with that brass, and while oversizing does reduce life, that's not a logical place for a split.

 

[918v]

Cases are going to split where they want to split, not where you want them to split or expect them to split.

 

[sawgunner2001]

I have no idea how the brass was cleaned by the vendor before I bought it. But since I’ve had it, it has been cleaned in a vibratory tumbler with LizardLitter and Frankford Arsenal case polish added to the media.

I think the smart thing to do will be to shitcan this whole lot and start anew.

 

[FLIGHT762]

There are bad lots of brass, it does happen.

Lessons learned: Use a comparator to F/L size brass to no more than .003"-.005" less shoulder bump than the brass fired in your gas gun.

When you F/L size brass by touching your die to the shell holder, you are just GUESSING as to how much you're sizing the brass. You have NO idea where you are. Comparators are great tools when you learn how to use them.

 

[supercorndogs]

CHS does not always happen low. I have seen them crack way up high like that before. I have shot a lot of that LC10 and 11 virgin brass from Natchez and never had trouble with it either.

 

[RldrNewby]

I don’t think the OP specified if he crimped or didn’t, but could excessive crimp cause what the OP experienced? The only reason I ask is am trying to learn as well. I haven’t tried crimping for my AR yet, but I’ve considered trying it sometime in the future.

 

[slowworm]

I don’t think the OP specified if he crimped or didn’t, but could excessive crimp cause what the OP experienced? The only reason I ask is am trying to learn as well. I haven’t tried crimping for my AR yet, but I’ve considered trying it sometime in the future.

No crimp. I only ever crimp my plinking ammo for my gas guns. I dropped my brass I was playing with and it dented, and then I realized about 30% of my cases got neck dents because of the concrete at the range.

Edit - This is not thread I thought it was.... I blame posting before coffee....

 

[spife7980]

No crimp. I only ever crimp my plinking ammo for my gas guns. I dropped my brass I was playing with and it dented, and then I realized about 30% of my cases got neck dents because of the concrete at the range.

How major are these dents? Got a pic? I’ve never noticed a dent that wouldn’t iron out in the sizing die itself. If it’s enough that a die won’t fix it then I’d say it’s trash

 

[lightman]

I'm going to guess and say that those cases were fired for their first time in some type of chamber with loose headspace. If so, the damage was already started before you loaded them. I've seen lots of cases fired in M-16's/M-4's that hit the ground looking like they were broken into. They were separated at the same places your cases are cracked.

Just for the heck of it, you might review how you set up your sizing die. But I really don't think this is from something that you are doing.

 

[918v]

Yes it is. He admitted he was sizing them too much.

With AR’s the thing is they bump the shoulder of the case as the bolt closes. So whatever amount of shoulder bump you thought you had is now tripled or quadrupled.

I set up my die for .002” bump so the bolt can be locked up gently if I want. The rifle adds another .004” if allowed to cycle normally.

If you want to maximize brass life you could set up the die not to bump at all but it would make the ammo unreliable for games or defense. But for range use it would work fine.

If you’re gonna do that then you have to determine the actual chamber length cuz the rifle will stretch cases and reading them is not going to give you reliable results. I FL size in .001” increments until the bolt can close on a round with finger pressure (upper off the lower). That’s my zero clearance point. Then I slam the bolt shut on that round and see how much the shoulder gets bumped. That gives you an idea how much the case is getting worked.

 

[slowworm]

How major are these dents? Got a pic? I’ve never noticed a dent that wouldn’t iron out in the sizing die itself. If it’s enough that a die won’t fix it then I’d say it’s trash

Duh - I'm replying to the wrong thread - I'm not the OP. Moral of the story - don't post before coffee has kicked in.

I win the dofus of the day award...

 

[TxWelder35]

Yes it is. He admitted he was sizing them too much.

With AR’s the thing is they bump the shoulder of the case as the bolt closes. So whatever amount of shoulder bump you thought you had is now tripled or quadrupled.

I set up my die for .002” bump so the bolt can be locked up gently if I want. The rifle adds another .004” if allowed to cycle normally.

If you want to maximize brass life you could set up the die not to bump at all but it would make the ammo unreliable for games or defense. But for range use it would work fine.

If you’re gonna do that then you have to determine the actual chamber length cuz the rifle will stretch cases and reading them is not going to give you reliable results. I FL size in .001” increments until the bolt can close on a round with finger pressure (upper off the lower). That’s my zero clearance point. Then I slam the bolt shut on that round and see how much the shoulder gets bumped. That gives you an idea how much the case is getting worked.

That’s interesting, I’ve never heard that. Going to go do some testing in a bit.

 

[whatsupdoc]

That’s interesting, I’ve never heard that. Going to go do some testing in a bit.

Never checked it on a small frame but on a large frame it does bump the shoulder.