Case Head Separation?

[blacklisted]

I recently decided to start reloading, and I have a problem that I am hoping someone here can help me with.

I prepared a bunch of once fired 5.56 NATO brass (Radway and Lake City) and found several that have a slight bulge near the base.

It is only noticeable due to the light marks left around it by the sizing die. My only guess is that it is the beginning of a case head separation, but I did not see any thinning in the area when I sectioned a few cases.

Cases with the 'bulge' will not chamber in my AR (.223 Wylde), and get stuck tight. Some of them have resistance when going in to the case gauge, and some will not go in to the case gage. They will chamber and extract from a bolt action rifle with a SAAMI-spec .223 chamber. The rest of the brass I prepared is fine.

Here is the procedure I used to prepare this brass:

1) Tumble
2) Lubricate (Dillon case lube)
3) Full length size (Redding die, adjusted to touch the shellholder)
4) Tumble briefly
5) Trim to 1.750
6) Swage primer pockets
7) Chamfer, Debur, and clean primer pockets

I did check several with a Lyman case gauge after sizing. They all checked out. It wasn't until I primed a small batch that I noticed the problem. Another trip through the sizing die does nothing.

The cases measure .377-.378 at the bulge. What do you think this is?

[Fjold]

Get a small base sizing die. Your die is not sizing enough of the case to fit your chamber. The marks on the case look like where your die is scraping them.

The gun that the brass was originally fired in has a larger sized chamber and is allowing the cases to expand too much.

[blacklisted]

Thanks for the quick response.

It is likely that these cases were all fired by the same rifle. It was probably wasn't my AR, because most of this brass went through it and most of it doesn't have this problem. All the brass was fired through three rifles (one mine, two belong to friends), and I can easily find out which one has the larger chamber and segregate that brass until I get a small base sizing die.

[PistolPete75]

make sure when you fullsize, you really fullsize. set the die all the way down untill your almost bottoming out on the case. remember to to use plenty of lube or you'll wear the brass out quickly.

on a different note, i only use certain brass on certain guns. i'll use mixed brass to shoot ar stuff, and i'll only use lupua match brass for my bolt action. i keep it seperate. i wouldn't mix brass if your shooting it in your ar15 and your bolt gun. you may also want to try using a different fullsize die like forestor.

are you also trimming your brass? that might be the culprit.

[blacklisted]

This is all for my AR, I don't have a bolt gun (the one I tested it in belongs to someone else). I'm just using the mixed brass for 55gr FMJ plinking loads. I tried setting the sizing die deeper, and it didn't help.

make sure when you fullsize, you really fullsize. set the die all the way down untill your almost bottoming out on the case. remember to to use plenty of lube or you'll wear the brass out quickly.

on a different note, i only use certain brass on certain guns. i'll use mixed brass to shoot ar stuff, and i'll only use lupua match brass for my bolt action. i keep it seperate. i wouldn't mix brass if your shooting it in your ar15 and your bolt gun. you may also want to try using a different fullsize die like forestor.

[PistolPete75]

are you trimming your brass? do that first, then go borrow someone's fullsize die and try it again. if your trimming your brass correctly, and fullsizing it correctly you shouldn't have an issue.

the brass you have issues with, throw them away. not all brass are created equal, and some may be really soft which will expand more than you want to. stay away from crappy brass. if you can find some guatamalen brass, it works well for plinking stuff. brass is strong, and can be reloaded many times. it's usually really cheep too. if you want to buy american try winchester brass. stop picking every piece of .223 brass at the range! hehee

[rksimple]

You might try screwing the die in another 1/4 turn past touching the shellholder. I've had a few dies that required that to get proper sizing, but that was mostly in the shoulder. I've never needed small base dies in any of my autoloading rifles (AR, Garand, M14,etc) and I've used all different kinds of surplus, "range pick up" brass.

[ocabj]

I personally recommend a SB die. You can get away with not using a small base die by screwing down the die until it firmly hits the shell holder (ram up) and then dropping the ram so you can turn the die another half turn.

But this has the side effect of sizing the shoulder far too much. *This* is where you'll get head separations.

I use a FL small base die for all LC that I get that is once fired and any Black Hills blue box LC brass. SAW fired brass is going to find it's way in any batch of brass that you get from a military range. As far as BH blue box, I've found that the brass hasn't been sized enough in the base area, probably because they sourced brass from SAWs and their resizing process didn't do an adequate job. Awhile back, someone gave me a box of BH blue box 77gr BTHP because they only had a 1:12. I tried it in a Wylde chambered WOA SPR barrel and half the cartridges wouldn't chamber completely. I checked them in a case gauge and several failed. I ended up letting one of my friend's at the range shoot it since he brought an original Colt "AR-15" that day with a very loose 5.56 NATO chamber.

[rksimple]

ocabj-usually when I go another quater turn from touching the shellholder, I get about .001 more in shoulder bump. It still comes out "in spec" compared to factory. Maybe I just got lucky with my die? I've only done this with my 223 die so it could be a fluke.

I helped a buddy begin reloading for his 7.82 Warbird, and it was absolutely necessary to put the die another 1/2 turn past touching. That would give us about .0015 to .002 shoulder bump. He even sent the die to RCBS and they said it was within spec. It really didn't seem normal.

I do agree though that if you're bumping the shoulder too much (and not checking with a comparator) there will be quite a bit of stretching in the web and separations will follow.

[m24armorer]

FL sizing for bolt guns, neck only for the BR folks. IMHO small base size for any selfloader. All my M118LR and MK262 are done on different dies and presses. 118 is FL and the MK262 is SB.

I also bump the die, a bit of contact between the shell holder and the die. I do make sure the shellholder is in spec otherwise the shoulder might not be in the right place.