Undersized 5.56 shoulder

[0hw0rd]

Bought 1k of once fired winchester 5.56 brass, prepped it, loaded it, checked OAL, overall ogive length, etc...all good, and took it to the range yesterday. None of the rounds (tried five or so) would fire and the bolt would lock up and need mortar'd to open. Seemed like a headspace issue, but I knew the bolt and barrel were good to go. Came home scratching my head, sat down at the bench, and took out the mic to check the case specs, to find the back of the shoulder on every checked round from the batch was .01" undersized, so the rounds were head-spacing off of the body. I had initially run all of them through a full length sizing die prior to loading, but again ran a handful through a forster bench rest sizing die to see if that would push them back a bit and push the shoulders out. No luck. All of the lapua and LC brass I had sized, mic'd/shot perfectly, so it's not a matter of poorly setup sizing dies.

Is there any way to pull these shoulders out to spec? Any help would be greatly appreciated!

ETA - The rest of the case mics in-spec from the front of the shoulder to the neck, and from the point it's head-spacing on the body, down to the head.

 

[CLP]

nvm

 

[119er]

I'm not really sure what to make of this. A picture sure would help.

First, I suggest using a case gauge from Wilson or Lyman, etc.

If a cartridge is undersized ant any given point I would think that is should at least chamber, but .01" seems like a lot. It sounds like you may have bumped the shoulder if you are crimping your bullets in a seating die or taper crimp die. That would cause the the dimension that I assume is directly below the shoulder to grow as it is displaced by the excessive travel into the die.

Otherwise you have over sized them to the point that they are no longer dimensionally correct, although that seems unlikely and would probably be pretty easy to spot. Being that it is commercial once fired brass I won't assume it was fired in a MG, so I say you do, in fact, have a die adjustment problem or you're using a wrong die.

Try to get a picture up of what you're talking about.

 

[0hw0rd]

The shoulder is .01" undersized, not oversized. It's chambering but going too far in as it's not headspacing off of the shoulder. I also checked brass from the same lot that I have not processed yet, and it's also .01" undersized at the shoulder. This is not a matter of me incorrectly sizing.

Eta - I'm not crimping the rounds and the shoulder to head length is correct, along with the OAL; the diameter of the shoulder/body junction is simply too small by .01". All of the case dimensions are correct except for the diameter at the shoulder/body junction.

There's nothing to post a photo of, as you can't see any issue with the naked eye.

 

[119er]

Let me get this straight. You're taking a fired (expanded) case and running it through a sizing die, yes? Said case is now undersized, and it's not the die adjustment or the wrong die? Has the gun been rechambered? Check the stamping on the barrel.


ETA: I think I understand the extraction difficulty, as you have identified that the case is undersized and it may be forming a slight wedge fit in the chamber near the shoulder area.

Also were these once fired cases bought as "prepped" cases that have been cleaned and possibly sized?

 

[downunderhunter]

He has answered that already, even his brass that hadn't been sized is out in that same way, and other types of brass size and fire properly. I'm sure someone can help you get the shoulder back in spec.

 

[0hw0rd]

I checked the unprocessed brass from the same batch that I have not sized yet and they're the same undersized diameter at the shoulder. The gun has not been re chambered and has zero issues with the lapua and LC brass I put through it. This issue isn't something I have caused...I'm just trying to figure out how to fix it so I'm not out 1k pieces of good brass.

 

[steve4102]

Your sizing die is not set up correctly.

You need to screw it into the press further. It should be screwed into the press until it touches the shell holder PLUS. Generic instructions are PLUS 1/4 turn to 1/2 turn more.

 

[119er]

Understood. I had a similar misforture a while back on some once fired brass I got but it was my fault on that one. They were sized just ever so off center apparently, and since they were sized to minimum I was out of luck. For me they weren't off enough to cause a problem and accuracy wise I don't see a difference. My point is, once you've got something undersized, firing it is about the only way I'm aware of to get them back out. Trying different dies and all with my cases didn't change squat.

I'd hate to think you'd have to pull those, but I'd try to find out what happened to that brass from who I bought it from. It will be up to you to determine if it will be safe to shoot those 1K rounds. Maybe a bolt gun? Mark the case with a Sharpie and chamber it to see where your interference is.

 

[0hw0rd]

Sizing die is setup correctly as previously stated. I even tried to push the shoulder down to see if I could push the shoulder out, but I bottomed the die out and it did not fix the shoulder. This is not something I did to the brass. It came this way.

I've reloaded 15,000+ rounds and figured out how to properly set my dies up quite a while ago. As stated twice already, the other LC, lapua, and even winchester (different batch) I have sized, was resized to correct specs and has been 100% trouble free. I'm not sure how many different ways to explain that the brass came this way and I'm trying to figure out how to push the shoulder diameter out.

 

[steve4102]

Sizing die is setup correctly as previously stated.

Sorry, but it can't be.

From your original post,

. None of the rounds (tried five or so) would fire and the bolt would lock up and need mortar'd to open. Seemed like a headspace issue,

Classic sign of an improperly set up sizing die. You need to bump the shoulder back more.

In all my years I cannot think of a single scenario where something "sized to small" would not fit and cause it to get stuck.

 

[243winxb]

bolt would lock up and need mortar'd to open. so the rounds were head-spacing off of the body.

Only if the web has expanded where the FL die doesnt size. I have fired ammo that measured .014" smaller then the chamber, when measured from head to datum. http://www.saami.org/specifications_and_information/index.cfm?page=CC Check the drawings. Datum is at .330"

 

[rcmodel]

In all my years I cannot think of a single scenario where something "sized to small" would not fit

Me either.

The problen has to be:
A. Either not sized correctly, (not pushing the shoulder back enough)

B. Or, crimping the bullet is causing shoulder collapse. (Most Like reason.)

But regardless of that.
1. The cartridge headspaces on an imaginary datum line halfway down the shoulder. (Not the outer top edge of it!)
And certainly not something you can measure with a standard caliper or micrometer.

2. The cartridge cannot get chambered deep enough to stick on the case body taper, if the extractor has hold of the rim.

3. .001" body taper at the shoulder (.355") over SAMMI standard (.3542") is not enough to cause any problems with stuck cases in any AR-15 chamber.

The fix is to color a sized case with a magic marker, chamber it, and see where the ink rubs off.

If it is a bulged shoulder from crimp?
A sized case will chamber, but a loaded one won't after it is crimped during seating.

IMO: It can only be caused by too much bullet crimp.
Either on purpose, or by accident because the seating die is adjusted too low and crimping without you being aware of it.
That in turn is bulging the shoulder and causing the loads to stick in the chamber.

Trust Me!

rc

 

[dmurdach]

I don't know if this would work, but i would try filling a few unsized cases with water and freezing them to expand the brass

 

[243winxb]

I'm not crimping the rounds and the shoulder to head length is correct, along with the OAL; the diameter of the shoulder/body junction is simply too small by .01". All of the case dimensions are correct except for the diameter at the shoulder/body junction.

Its head to datum that matters. http://www.brownells.com/.aspx/lid=12897/GunTechdetail/Gauging_Success___Minimum_Headspace_and_Maximum_COL

 

[steve4102]

Me either.

The problen has to be:
A. Either not sized correctly, (not pushing the shoulder back enough)

B. Or, crimping the bullet is causing shoulder collapse. (Most Like reason.)

He also said this on another forum.

The rounds will not fire, as they're going almost a half inch too far into the chamber and the pin isn't even coming close to striking.

No way a 223 case, no matter how the FL sizing was butchered, will it go a Half and inch to far into the chamber.

 

[rcmodel]

Oh really!

I did not know he said that on another forum!

Definitely Way More going on here then was stated in the OP!

Sounds like a .221 Rem sizing die got involved somehow!
Thats nearly 3/8" shorter!
And the case would measure .007" larger at the shoulder then a .223 case.

Rc

 

[CLP]

And you're sure the AR you're shooting isn't a non-5.56 chamber? Like 6.8 or .300?

 

[steve4102]

There's nothing to post a photo of, as you can't see any issue with the naked eye.

If you cannot see a problem with the naked eye, yet it enters the chamber almost a full half inch to far, then the problem is not the sized case.

 

[Walkalong]

.223 rounds cannot head space off the body. No .223 sizer made will push the shoulder back .5". You need some sort of case gauge or comparator to check shoulder position. If the cases won't chamber, usually it's the shoulder that is not back far enough, or the case is bulged near the web, or the shoulder is buckled a little.

We need some better information.

 

[higgite]

There's nothing to post a photo of, as you can't see any issue with the naked eye.

Photos are always helpful, even if only to confirm what's not wrong. Some of these guys sneeze at 15,000 rounds. You asked for their help, give them all the info you can, even if you don't think they need it. And please include a pic of the offending cases' headstamp and some reference to scale of the sized cases and finished rounds. A half inch short is pretty astounding. I'm sure we would all like to see that.

 

[243winxb]

M862 5.56mm Short Range Training Ammunition (SRTA)??

The other thread - http://www.ar15.com/forums/t_6_42/423965_Undersized_win_5_56_shoulders.html It almost sounds like a 221 fireball like RC said. Brass goes into the gage about 1cm, so OP said. Thats about .393" to much shoulder set back. Very strange??? From other thread, could it be

M862 5.56mm Short Range Training Ammunition (SRTA)

?? http://www.armystudyguide.com/content/army_board_study_guide_topics/m16a2/ammunition-types-and-char.shtml When a light powder charge is used, the body may expand outward. This pulls the neck/shoulder back, giving a shorter head to datum measurement. But i can't see it doing .393" if OP is correct in his statement??? Only problem is, looks like a steel case or something other than brass?? Photo here shows brass - http://www.ar15.com/forums/t_3_16/247139_M862_Short_Range_Training_Ammunition__SRTA_.html

 

[steve4102]

^^^^

But if it were 221 you would be able to see it with the "Naked" eye.

The OP says he cannot see any external case variations with his Naked eye.

A 221 compared to the 223 would indeed be visible with the "Naked" eye, yes?

 

[rcmodel]

Yes it would.

But if it goes in the chamber 1/2" to far, won't fire, and gets stuck so the bolt won't open?

That should be visable to the 'Naked eye' too, yes?

rc

 

[steve4102]

^^^

Exactly, so none of this makes any sense and I'm starting to think it is a Leg pulling exercise.


Edit:
If it entered the chamber a half inch to far, the bolt would not be stuck as there is no way the case head is still in contact with the bolt. The bolt would open, but the case would remain buried in the chamber.