Home Forums Reloading Big Game Rifles Why. Split cases above the magnum belt?

See pic link below. This happened at the range today. Could this be brass that’s loaded too many times? Yes, I don’t keep very good track of how many times I load my brass.

I usually adjust the die to size the neck only, then give it another 1/8 turn down.

Thanks for your expertise!

Brass pic. 7mm rem mag

I shoot my 7 mag brass 3 times, junk it after for that reason. I have four 7 mags, so I full length resize my brass.

You’ve resized them way too much. Chances are you were resizing way more than the neck. Without a way to measure headspace you’re guessing at how much you’re resizing.

Belted magnum cases all need fireformed to get the best case life. If you don't, then you get exactly the results you have. A case head separation. My .300WM brass when new had a shoulder that was over .040 back from where it ended up after firing. Get new brass, take about 3grains of powder out of it, load some heavy 200gr or 220gr bullets out until they touch the rifling. 1/8th of a turn on a 7/8-14 die will move you shoulder back almost .009, which is way too much. Run it down until it touches, then just a taste more. Check to see if it chambers. If not, then just a bit more until it does. .002-.003 is what you're aiming for.

Thanks all. What’s the consensus on sig brass? Seems to be about all that I can find available?

How do you adjust your FL die to just size the neck?

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Yup. That's a case head separation, not a split. Case head separation happens when the case is repeatedly shortened in reloading, then stretched in firing. You might try a Lee neck collet die to avoid this.

Yes, generally you go by fired case size and then just bump the shoulder a minute amount. I'm not a neck sizer, as I like my ammo to be 100% reliable out in the field. My belted magnums are ones that go out in the field, so this really applies to them. Even if a guy doesn't have a comparator, he can adjust the die so the sized brass has a slight bit of tension when chambered. That is generally around a .001-.003" bump. Good enough for the girls I hang out with and reduces case stretch so you can get multiple loadings on the brass. Op also asked about Sig brass. It has been excellent for me thus far.

It would also be interesting to know how far forward the shoulder moves when the brass is fired the first time in that particular chamber.

Me as well. Betting it is a pile..

Agree with everyone above; its time to buy a comparator so you know exactly how much you're setting the shoulder back.

I've been around some doozy 300 Win mag chambers.

A piece of 40 S&W brass will work fine.

Interesting. I had not thunk of that.

As with non-belted brass, size just enough so that a cartridge will chamber with slight resistance. After three or four such sizings, the brass will probably will require a full-length sizing then you can start over with the partial sizings.

I’ve been loading for this rifle for a long time without issue. Only recently I started going 1/8 of a turn past the neck only because I had a couple that were almost too tight to chamber. I also changed die sets when I did this. I’ll go back to my old dies and old methods, and get new brass. Some of this brass could have been loaded upwards of 5,6,7 times, possibly more.

I create false shoulders for the virgin firing in my belted magnums (along with most every other chambering) for this reason.

I neck size only, but brass has to remain rifle specific.

On my press, a full turn of the seating stem is .060". If you tightened down 1/8 turn, that's .0075", quite a bit too much.