Thread: Split brass

Any ideas what is happening to my 7mm rem mag brass. Not running huge pressure/load but the base of the case is splitting a few mm up from the belt to varying degrees. On their 3rd load and annealled between 2nd and 3rd

Case head separation can be cause by over sizing them

Originally Posted by Kelton

Case head separation can be cause by over sizing them

I am only bumping shoulder by 2or3 thou, should I just be neck sizing

Originally Posted by nigelp

I am only bumping shoulder by 2or3 thou, should I just be neck sizing

Greetings @nigelp,
How are you measuring your shoulder bump? It takes a lot more than 0.002 to 0.003" of shoulder head space to crack a case like that in three shots. Belted cases can be an absolute pig for head separations due to the belt recess in the chamber being too large for the actual belt. The case can still chamber hard with the shoulder sized to fit in the chamber. The only fix for this is to size the case body just in front of the belt separately from the rest of the case. There is a special tool for this but a friend got by with his .308Norma Mag by using a .300 Win Mag die that only sized the base. Some case makes can be bad for this. Others should be able to comment further on this. There is a reason that all the latest hot shot cartridges don't have a belt.
Regards Grandpamac.

only bump it as much as you need to be able to chamber freely..... and PLEASE paperclip test ALL your brass before loading it up from here on in.....
its a real pain in arse if you get a seperation on day one of a hunt....or at any other time....

Paper clip test being feeling for a bump inside the case where the split is then checking other cases for the same bump?

Interesting I believe this is also a contributing factor in people not liking belted cases I never had the issue with 7RM I lost my brass pretty quick though. Nope neck sizings the pitts . Their is a particular die for belted cases but I’m not clued up on what the go is their sorry I wouldn’t a clue how much shoulder bump I’m giving I set my die so the bolt just closes freely and call it a day . That also may be considered a lot of shoulder bump if you have gone that far from new?

Should be able to run the paper clip up and down the inside of the case with no snagging is my take on it

sharp pointy paper clip with a right angled bend in end about 3mm long...scratch the inside of case as hard as you can....if there is a fault it will "catch" try it on the ones that are buggered and you will soon feel what the go is.

Have you had to trim them?

Originally Posted by JohnDuxbury

Have you had to trim them?

Yes I trimmed them at 2nd firing

Get a cheap set of oring picks. Think I got mine from workshopinnovation.co.nz.
After my first separation I started checking all my brass for that particular rifle.
Sav 99 in 243 with a tight chamber could see a ring forming on the outside.
Dumped all that old brass as well and started with fresh stuff.

2-3 reloads does not seem like a lot. Lots of possible causes, try a different brand of brass next time. And only size just enough to allow the bolt to close.
I will sometimes take one case and starting with just neck sizing it and checking to see if it will chamber, if not then start gradually bumping the neck until it Chambers.

Nb my other sav 99 and the bolt actions I load for have never had a problem.
Z

Any pictures of the case head?

What's your cleaning regimen like as a dirty chamber can cause overpressure issues as well.

Looks like there's a hole in that case to the right?

Originally Posted by Rated M for Magnum

Any pictures of the case head?

What's your cleaning regimen like as a dirty chamber can cause overpressure issues as well.

Looks like there's a hole in that case to the right?

Will post up a pic tonight of case head - I clean the rifle every 25 or so rounds.

No pressure signs on primers. The case has a small hole after last firing on the right side case

It sounds like your sizing is ok but you could bump the shoulder less to try and improve the life of the brass.
What brand is the brass?
It could be that the rifle has generous chamber and or headspace dimensions and most of that streatch is happening on the first firing.
What does a new vs fired case measure to the shoulder?