mushroomed case shoulders

[ham385]

Hi,

In my last batch of .223, I came across a case that wouldn't feed, and actually got stuck partially in the chamber. It took quite a bit to get it out, but luckily the bolt extractor did it's job without any additional tools.

After inspecting it, I found that part of the case had mushroomed out slightly. Not enough to notice in a cursory look, but enough to cause it to bind in the chamber. I think the section where it mushroomed is called the shoulder. It's below the neck, after it tapers out, and where it joins into the straight walls of the larger diameter section of the case. Imagine if you took an empty case, stood it up on end, and pushed down on the neck enough to slightly deform it, and that's what I had.

I wish I had a picture, but I didn't keep any of them.

This scared the crap out of me. All I could think about is what would have happened if the bolt (AR15) were out of battery but rotated far enough to allow it to fire.

These cases were on their 2nd firing, and were full length resized. I use a lee autodisk charger, so it's my prime suspect. It just seems like a lot of spring tension to move that disk back and forth. I also thought that maybe the seating or crimping may be the culprit, although, I was using FMJBT, and they slid right into the neck with nearly zero friction.


Anyone ever encounter or hear of this? Any tips on how to avoid it?

Edit: oh, and out of the batch of 100, I found 4 like that.

[bogey1]

over crimping is what comes to mind. Ive done it with the 50 a few times.

[Buckster]

I have done this before. I did it to some 7mm mag cases. The problem for me was that the bullet seating die was down too far. I think that with it down you can use it to add a roll crimp to cases. I would try backing off the die a turn or 2. After you do that you will have to adjust your seat depth again.

[smitty56]

That is one of the reason you always have a case guage when you reload.
Here is a link to one.

If your reloaded ammo will not fit in the case guage, then you are doing something wrong that swells out the case beyond specs. Member Bogey in a message before mine named one thing that might be happening.

Case Gages are a "go/no-go" gage for a loaded round. Or in other words, if a loaded round drops all the way into the Case Gage, it will fit in your handgun's chamber.
Dillon's Stainless Steel Case Gages are made to SAMMI minimum chamber dimensions and are accurate to within plus or minus .001" - which allows you to quickly check all critical dimensions of your loaded ammunition, including maximum overall cartridge length and base diameter.

.....says the Brian Enos web site at:
http://www.brianenos.com/store/dillon.dies.html

Also just do a search for "Dillon Case guage in Google.
You will get a lot of hits to help you.

[Flash]

This condition most commonlly occurs in crimping.

Ther main cause is that not all your cases are at uniform length when you insert bullet and crimp. You set up your bullet seating and crimp on your first case of the batch, and if that case happens to be a bit shorter than some others, it will be fine for the short cases, but when you run the longer cases to the full stroke of the press, the longer cases will experience a more firm crimp, thus pushing back on the neck (right at the crimp point) and the easiest place for the case to give is the shoulder, thus bulging the shoulder while it sets it back, too.

You should solve this by making sure each batch has the same empty case length. Thus, each bullet-seating/crimp operation will result in the same crimp, the same COAL, and no shoulder-bulge.

Now it does not matter if each batch has a different length (unless you are REALLY after precision, like 400-yd bench rest - we're talking of blasting fodder, here, aren't we?) as long as they are within specification. There is a tolerance for minimum-to-maximum trim length. Just make sure that each batch is within that tolerance range and 0.010" or 0.015" of each other, when you set up the die for bullet seating and crimping, just use the longest case, and go to it. Set COAL within tolerance, then adjust the crimp. This will assure you of reliable, functional plinking ammo. You won't collapse shoulders, you will have a functional crimp. Cheap, but very good, calipers for this purpose can be had from Harbor Freight ( http://search.harborfreight.com/cpis...igital+caliper ), and I like item # 47257 at $29.95. It goes on sale at $12.95, frequently.

When you aspire to more precision shooting, you will need more precise ammunition, and by that time you will have established a process that includes uniform cases.

You mentioned that you full-length resized these cases. You may find, by experimentation, that neck-sizing only will be acceptable for your rifle. If you fire the cartridges in the same rifle, it may work for you, though the caveat is that cases for semi-autos be full length resized. Bolt-guns are far more tolerant of length conditions, as the camming action of closing the bolt can close it on a case significantly deformed. I load 5.56 for an AR and a Mini 14, and I find that I can "almost" full length resize, and that ammo works well in either. I think it extends brass life, and it works for me. I AM talking "blasting fodder" though, here, and not precision 400-yd stuff. However, I am fussy about trim-to-length, as it makes both the process easy, and the finished product functional.

Keep shooting.

Flash

[Koli01]

I have done this before. I did it to some 7mm mag cases. The problem for me was that the bullet seating die was down too far. I think that with it down you can use it to add a roll crimp to cases. I would try backing off the die a turn or 2. After you do that you will have to adjust your seat depth again.

This is what I've experienced before. Not sure about crimping as I don't.

[Mootness]

What Flash said, you've got a die set in too far and it's crushing the cases.

I've done it before too. oops.

However I don't quite agree with neck sizing for your semi-auto ar, but maybe it has worked for Flash. Read your manuals, in the front, they'll talk about setting up a full length resizing die so that it only bumps the shoulder back *just enough* for your semi auto to extend case life. This is only good if you're using the cases in only 1 gun, & keeping track of that.

[ham385]

Thanks to all for your replies.
I'm using 2 dies, the forster seating die (which also roll crimps if turned down enough), and the lee factory crimp.

Flash, you explanation makes perfect sense. I did not trim this batch after resizing so it is pretty likely a had some good variance. I had set the seating die to not do any crimp, but with very little tolerance. If I got a long case, It would have been crimped by the seating die, and the factory crimp die would have pushed it down, mushrooming the case.

This fits in with what everyone else said about backing off the die a bit too.

Smitty, I do think the case gauge will be one of my next purchases. I previously thought of it as a gadget I do not need.

I'll take all of your advice on my next batch. I'll back off the seating die a bit, measure and sort my cases, and will get the case guage. I will let you know how it goes.

This ammo is just for plinking, I haven't even worked up a load for accuracy, I just started a the minimum, and went up until I got good functioning out of the AR.
Do all of you trim every time you resize for plinking, or just every 3-4th reloading?

[hzox221]

Another cause may be that it was fired in an unsupported chamber. A full length sizing die would solve it.

[Flash]

Thanks to all for your replies.
..

..


This ammo is just for plinking, I haven't even worked up a load for accuracy, I just started a the minimum, and went up until I got good functioning out of the AR.
Do all of you trim every time you resize for plinking, or just every 3-4th reloading?

I check case length first. I only trim those which exceed maximum. Then they become another - separate - batch. It's kind of a "judgement" thing, here.

When doing a batch for a powder test or where consistency and "real" accuracy are desired, I just go ahead and length-trim every one after resizing. Uniformity is the key here.



Flash