I had a 243 case separate today.About 1\3 of an inch above the case head. Lapua cases,the 10th firing. They have been annealed twice,the last time between the 8th and 9th firing.41 grains of H4350. Pushing a 105 bullet at 3000fps. Anybody else experience something similar?Thoughts? Also this is about #700 in the round count with this load, so it is not new.

Hopefully annealing or not had absolutely nothing to do with that far down on the cartridge. If so, that explains a lot.

What sizing procedure? Neck or FL sizing with minimal bump? Brass is going to flow and stretch after multiple rounds no matter what. And they also harden where they cant be annealed.

10 full load firings isnt really anything to complain about. Lapua is great brass, but it still has a lifespan of some sort.

Old + tired brass, or oversized a bit.
Time for new brass, or you'll be worrying about it happening every time you chamber a round.
You can also take a piece of wire or a dental pic and scrape/run it up inside the base area.
If you feel it catch around that 1/3 rd " area, toss it.
Had the same issue with 50bmg brass.
Never had an issue with Puny caliber brass.
I had to make witness marks on the die and press to make sure I had the same setting.
I found that I was turning the die in a couple thousandths while switching between die.
I trusted that the lock ring was infallible and learned the lesson the hard and expensive way with 100 match primed/prepped 50bmg brass.

Redding competition dies. Full length resizing. Thinking the brass had reached its fatigued point. I have taken a couple of batches of Lapua brass to 12 or 13 firings though. No issues with them.

A significant reason for that case body separation is excessive FL sizing, or a over size chamber (too much headspace).

Reset your F.L. sizing die!

FL size a fired case with the die screwed way back out in the press.

Try the sized case in your empty chamber by closing the bolt on it.

The bolt should NOT close.

Screw the FL die down just a little bit and FL size that case again.

Try it in your chamber again.

Keep sizing it down a little at a time until the bolt just closes on that case.

NOW the FL die is set!

Of course you can size the cases down just a little bit more by screwing the die down a tiny bit more so you can just feel the bolt close on a new FL sized case!

Are you setting the shoulder back too much? Case head separation is usually a result of stretching the brass.

I would suggest new brass and neck sizing.

37.5gr of H4350 giving a 105gr A-Max a velocity of 2,799 is a max load on Hodgdon's web site. 700 rounds with 41gr of H4350 makes me think you should have your head space checked.

Thanks for the input so far.I think hodgdon is playing it a little bit safe. I know its pretty common to run a couple grains more, and 100 to 200fps faster than what I am running now with 105s. I may check my head spacing though. Haven't had pressure signs that I can see either.

Dude, not seeing pressure signs means nothing. You are 200 fps beyond Hodgdon's max speed for 105's which means you are over pressure.

Buy some new brass and some IMR7977 if you need 3000 fps.

Velocity IS your FIRST PRESSURE SIGN. Maybe "indicator" is a better word. But relying solely on visible pressure signs on your brass, or bolt lift, is living pretty close to the edge...and especially if you already know your velocity is up there like that, powder type taken into consideration.

Thanks for all the info.I appreciate it.

Yep,

That's why.

Start over with new brass and neck size. The more you work your brass the quicker you will wear it out. Also, get yourself a Redding body die. On those occasions you do need to set the shoulder back a bit you will have better control and again be able to minimize how much you work your brass.

This is not how it works. Just did a batch of PFL yesterday. A die backed out one full turn (or more) will chamber (if it chambers before ever going into the die). It's when you get within about 1/8 to 1/16 of a turn from touching the shell holder that you've squeezed the case body down enuff that it pushes the shoulder forward. I've confirmed this with multiple FL die sets and chamberings.

Imagine that.

I visited with the gunsmith that built the rifle and helped develop the load.Simply put,while the load is not too hot,it is hot enough to wear the brass out quicker,and 10 firings,might be pushing the end,if I continue to full length resize.Likely neck sizing would buy a couple more firings. He also said that the brass will show a ring above the web when it is getting weak, and that the brass in this area can get brittle over a lot of firings,because it is not annealed. Thanks again for the input.

Just to make sure it's clear: the bright ring you mention is very near the case head. Annealing should NEVER have any effect on brass in that region, it is only for the neck/shoulder area. The area of stretching near the case head does get brittle because it is being worked as the case stretches and becomes thinner.

Here's a nice shot of the different stages of head separation [img:center][/img]

An easy way to check your brass when they're in process is a paperclip, sharpened and bent then drag it over the head area inside. This one shows how the brass is getting thinner and you can see where the clip has been dragging in the groove [img:center][/img]

Is your life and accident insurance paid up?

Excellent pictures.The guy who helped me get the case out had a brass wire like yours for testing and I could tell on a couple of his old cases,where the ring was. We readjusted my sizing die a bit. I think this was probably the issue. In visiting with Pat Sinclair,he thought so too.His load is a couple grains hotter in the 6 creed with the same bullet and he is on13 firings on his brass.I will start out with new brass on the next batch. Thanks again for the info.

Case head separation is not usually associated with loads that are too hot. It is normally associated with stretching the brass in the chamber and shortening it in the full length die.

That is what we figure the slight misadjustment of the die caused.It was slight,but likely enough to cause the problem.

You might like the Lee collet neck sizing die. No muss, no fuss, never sets the shoulder back, and brass lasts a very long time with just a little annealing.

Some excellent advice here but, has anyone heard of, or used the Skip's die shim kit for partial resizing?

It consists of 7 precision ground washer-like spacers which fit between the sizing die lock ring and the top of the press. You just set up your die, as per the manufacturer's instructions, then experiment with the spacers until you get a slight resistance when closing the rifle action. Make sure to start with the thickest spacer. If the action won't close, or feels too tight, try the next thinner one. Repeat until you get the right "feel". Single spacers or any combination of spacers can be used. Once you get the right combo, make note of it in your data. You'll never again have to fiddle around re-adjusting your die between FL and partial sizing. Slick as a whistle. They're not expensive and are available through Sinclair International.

The same thing can be accomplished using automotive (spark plug) spacers but you should have duplicate sets so you can put an equal spacer on opposite sides of the die to ensure that all is square with the world. I did it this way for years until I heard about the Skip's spacers, which are much handier.

I saw these yesterday. The guy that helped me get the case out of my chamber had them. They worked just as you explained,and he loved them.

$12:99 at Sinclair's International. Ya can't go wrong.👍