Brass cracking just behind shoulder

[RobRat]

I'm on my 5th loading of a batch of 300/221 brass, and am finding cracks just behind the shoulder on a number of the cases. The cracks run about 1/2 way around the circumference of the case, on the straight part, at the edge of the shoulder, just past the radius.

I started with Lake City 07 5.56 brass, cut them off just behind the shoulder with a Harbor Freight mini chop saw, formed into 300/221 with a Reading sizing die, then final trimmed to length.

The rifle is an AR-15 upper, that I had a gunsmith friend of mine build for for me.

I thought that I might be bumping the shoulder excessively, and am finding that I'm bumping the shoulder about 0.004", which I'm thinking isn't excessive.

I did not anneal after forming- -could this be the cause? would this help?

Is there better brass to use to form the cases with?

[HUNTER2]

I anneal all my brass after forming, but I am not using an ar. And anneal again after 5 loads. May be excessive..Have some that is closing in on 20 loads and when sizing the shoulder is just barely touched. Some had rather get new brass than anneal. Most of mine is LC brass. Hope this helps...

[Hoser]

I did not anneal after forming- -could this be the cause? would this help?

Is there better brass to use to form the cases with?

Annealing *if* done right, cant hurt and might help.

I have used Lake City brass for ages and it is pretty good quality. Lapua and Winchester 223 is better, but they come at a pretty high cost.

I have lots of Whisper brass that I have reloaded 10+ times (subsonic) and have not had any case separations or brass growth that required trimming.

[snipecatcher]

I annealed a batch of 20 pieces of brass for my bolt gun after 3 reloads. You can definitely tell a difference when resizing the cases. I found that it is necessary to anneal my 6.5x55 brass after 3 loads because the chamber is oversized and my dies were working the brass too much. I've since switched to collet dies, but have not shot that particular rifle enough to worry with annealing in quite some time. I used the cheap Hornady kit with the Tempilaq paint and heat sinks that you chuck into a drill. It seems to work well enough, but it's a PITA if you've got a lot of brass to do.
-Dan

[i8asquirrel]

I just finished forming and loadimg 500 rounds of LC brass I baught from Natchez Shooters supply. I was chopsawing and forming brass. On this batch I sized in two steps 1st to about 26cal then to .308.left the cases full length and then trimmed with Hornady Camlock trimmer hooked to my cordless drill. It worked great. Out of a batch of 509 cases I lost 3 to splis!!

[i8asquirrel]

I just finished forming and loadimg 500 rounds of LC brass I baught from Natchez Shooters supply. I was chopsawing and forming brass. On this batch I sized in two steps 1st to about 26cal then to .308.left the cases full length and then trimmed with Hornady Camlock trimmer hooked to my cordless drill. It worked great. Out of a batch of 509 cases I lost 3 to splits!!

[tp555]

I got 5 reloads before the necks separated on mil brass without annealing.

[amafrank]

I normally anneal the big stuff like the .338, .50cal and the 20mm but I've never annealed the 30-.221. I've got some cases that have been fired at least 12 times since conversion from .223 to the 30 and never had a case split for any reason. Even the cases I was using to test the high velocity stuff has been fired 7 or 8 times and still no splits...I have had some primer pockets open up though.
Maybe the problem with your splitting is due to a large chamber and a small die. ..

Frank