trouble with lapua 221 fb brass

[MIKEL]

Was shooting my 20vt yesterday and a piece of lapua brass broke in half and stuck in the chamber.The case was loaded only about 4 times .it is not a hot load . it was 17.9 gr of 4198 and a 32 gr nosier varmagedon. was lucky enough to get the casing out by banging the riffle but on the ground.Has anyone else had trouble with Lapua brass?

[TinMan]

If the break is around the body of the case, that is a classic sign of the case being resized too short. Another test is to use a piece of a paper clip bent into a short "L" shape so you can reach inside of another fired case, and try to feel if there is a thin spot in the brass (like a ring) at the height of your broken case.

[MIKEL]

Break is about 9/16 above case head.I have another case that has a slight ring at about the same place.i ran an allan wrench inside the case and i can feel some sort of break.thank you

[MIKEL]

DO you mean case oal?I have case sized to 1.3925 it calls for 1.395. would that little cause this problem?

[JohnHenry]

Originally Posted by MIKEL

DO you mean case oal?I have case sized to 1.3925 it calls for 1.395. would that little cause this problem?

The problem you encountered can be caused by bumping the shoulder back too much when you resize. In a bolt action, I set-up the resizing die to bump the shoulder of the fired case back .001 to .002.

PS: FYI http://bulletin.accurateshooter.com/...shoulder-bump/

[SmokinJoe]

MIKEL, you are sizing them too much and creating excess headspace which stretches the case a little more each time you fire it. Are you screwing the sizer down to touch the shell holder? If that is what you are doing, it probably is a case of tolerances stacked negatively so that the setup sizes the case down too much headspace wise. Do some research om bumping shoulders and I think you will gain a better understanding of what is going on. Hope this helps, what you are experiencing is certainly no fun and can be dangerous.

[flyrod]

As others have pointed out, the cases are stretching significantly in the chamber when fired, causing the split. The basic remedy is to make the brass fit the chamber better.

A couple other factors to consider: what rifle are you using? I've noticed that Contender frames stretch much more than a bolt action, and even with a 22 Hornet I get less case life in the Contender. Even with brass that perfectly fits the chamber, the frame flexes under load and the brass along with it. Also, how are you forming the 20vt brass? You could be seeing most of the stretch on the first fire-forming. I have a 243AI that would crack cases on the first firing of new brass this way. I eventually found a way to form the brass better to solve this.

[MIKEL]

Thanks guys.Thats what I've been doing wrong.Ive been setting die so the press lever wratches over. probably to low.Thanks for the help..Iwill set the die up a bit

[MIKEL]

yes i thought of that also..shootin the round in a model 21 cooper rifle.been fire forming with 34 gr dog town over 17.9 gr h335.because the cooper has a .232 chamber and i don't have a neck turner i have been inside case reaming with a .224 reamer on a fired case.

[SmokinJoe]

The recommended article looks pretty good so it should help you. Something to remember about bumping shoulders with a FL die is that as you approach shoulder bump the headspace will actually get a little longer because the brass has to go somewhere as your die squeezes it down, then you will go past that point to the point of actually reducing the headspace back to what you want. Once you get the die adjusted to that point, you are controlling the headspace and can easily adjust for more or less from there. So this is what is gonna happen when you start adjusting your die to get that correct shoulder bump. First you back the die off about a half turn, then size a case and see how it fits in the rifle. Repeat this step turning the die down a little each time (re-lube the case every time to make the sizing action consistent). At some point before you get back to the die touching the shell holder, you will feel the case get tighter as you close the bolt than it was before you sized it. Adjust the die down a little more and see how it feels when you close the bolt. You have to keep doing this a little at a time until the resistance on closing gets a little easier, at which point you should be near zero headspace. Now adjust the die down just a little more and you should be able to close the bolt easily and should have found your setting. Lock the die ring down so your setting is retained. You would do best by getting a good set of digital calipers and a Hornady headspace gage setup so you can actually measure what is happening. The main thing to accomplish is not getting the case too loose in the chamber (excess headspace) like you have apparently been doing. Hope this is clear enough. If not keep asking questions and you will get it figured out. The first time anybody bumps shoulders, you will learn a lot.