Thoughts on split case necks?

[Juicymeat]

Anyone happen to have any insight as to why my case necks are splitting so soon?

I'm using two batches of Lapua brass, one batch 2x fired, the other 3x fired. Splits happened with cases from both batches after FL resizing and not after firing as far as I can tell. Normally I wouldn't care too much, but since it's Lapua brass it should last longer than just two firings from reading about other forum member experiences.

Gun is a stock Remington 700 with 20" barrel pushing a 178gr amax 2760 fps in 75 degree weather. Currently loading 47.6 grains of 2000mr with a COAL of 2.810

[Carcassonne]

My guess is the brass is too brittle. It has become very common these days with many brands. Some of my Starline 10mm split the first time it was fired. I had some SIG brass that split the 4th time it was fired.

Could be bad heat treating and/or anealing, or it could be everyone is buying their raw material from China. It could also be some chemicals in the polishing media like amonia.

I didn't see brass split this much 20+ years ago.


.

[Whiterabbit]

I see brass split like this.

In my experience (data point of one person), splitting in the middle like this is caused by overworking the brass.

Specifically, sizing it down too much in a die that is too small, then expanding it out too big in a chamber cut too large. Like your die was the last one cut on that reamer, and your chamber was the first cut on a new reamer (or is OOS big). Or a combination of either of those two.

Seeing the split near the shoulder, it could also be a sign you are pushing the shoulder back way too far. Again, this would be a bad die or a bad chamber, or edge-of-spec thing, or a combo.

That's what I would look for. I'd find some range pickup brass and measure to compare. Maybe headspace the rifle vs another one I had, or a friends, or inspect their fired brass.

But those are the two (four) trees I would go barking up first if I were in your situation.

---------

edit: looks like the first two splits are nowhere near the mouth or the shoulder. I'd definite start by looking if I was overworking the necks by sizing them down way to small in the die, and blowing them way too open in the rifle.

[bsumoba]

I had some Lapua brass split like this early on (maybe 2 cases only though out of 300 cases). I started annealing frequently and the problem went away.

My chambers are cut with about 0.004"-0.005" neck clearance, so I "blow" out my necks quite a bit every firing. I also bump the shoulders back about 0.002-0.003" so that coupled with the neck clearance is not prematurely splitting necks. I just retired my brass and it went through about 15+ firings each.

[Juicymeat]

Thanks for the info guys, I'll play with my sizing die and see if that helps any. Plan was to anneal after the 4th or 5th firing but I may as well do it now.

Out of curiosity, how do you guys set up your FL resizing dies? For pistols I normally bring the ram up, screw the die down until it touches the shell holder, then go another 1/8th to a quarter turn down. I've done the same for rifles and am wondering if the last step is causing the brass to be slightly undersized like y'all are saying.

[SixPointEight]

What dies are you using?

To me this is probably cause by overworking the brass. Standard dies will squeeze the neck down, then expand it back to size. And if you screw the die in all the way, it's setting the shoulder back to SAAMI minimums. I set my sizing die up to bump the shoulder only .003" (takes some trial and error). Dies with neck bushings could help.

But the single best thing you could do is to anneal the brass. If it's splitting from being overworked, then it's getting hardened and you'll have inconsistent neck tension on your loaded rounds which has a direct effect on accuracy

[Whiterabbit]

Thanks for the info guys, I'll play with my sizing die and see if that helps any. Plan was to anneal after the 4th or 5th firing but I may as well do it now.

Out of curiosity, how do you guys set up your FL resizing dies? For pistols I normally bring the ram up, screw the die down until it touches the shell holder, then go another 1/8th to a quarter turn down. I've done the same for rifles and am wondering if the last step is causing the brass to be slightly undersized like y'all are saying.

Unlikely to be your issue. If you are over-sizing your shoulders by bumping them back too far for whatever reason, you should see the overwork splits at the shoulder. You aren't. You are seeing them in the neck. That's a die or chamber dimensional issue (bad brass? etc) issue rather than a die setup issue.

If you changed your setup to neck size only, backed off on the FL die, etc, but made no geometry change, I would expect the split necks to continue.

On the other hand, simply replacing the die might help as well. If you have a friend with a die for the same case, you can run 10x through your die, 10x through his die, and measure the necks with a micrometer (no expander plug). That will tell the tale. That, and comparing the fired brass between rifles.

[FLIGHT762]

Out of curiosity, how do you guys set up your FL resizing dies? For pistols I normally bring the ram up, screw the die down until it touches the shell holder, then go another 1/8th to a quarter turn down. I've done the same for rifles and am wondering if the last step is causing the brass to be slightly undersized like y'all are saying.

If you're not using some kind of gauge to show you how much your F/L die is sizing the brass you're just guessing. Sure, you can use your rifle's chamber as a gauge that works, but it is time consuming.

Much easier to use a gauge and get it exactly right.

[OpenSightsOnly]

Thanks for the info guys, I'll play with my sizing die and see if that helps any. Plan was to anneal after the 4th or 5th firing but I may as well do it now.

Out of curiosity, how do you guys set up your FL resizing dies? For pistols I normally bring the ram up, screw the die down until it touches the shell holder, then go another 1/8th to a quarter turn down. I've done the same for rifles and am wondering if the last step is causing the brass to be slightly undersized like y'all are saying.

Go buy the Stoney Point / Hornady cartridge headspace gauge.

You can use that to measure the brass length of your fired brass and use that info to set up your die.

[Juicymeat]

Currently using RCBS dies, but I do have a buddy who has some Lee dies I can borrow. I'll size some brass using both and see what kind of measurable differences there are, if any. Thanks for the help and equipment recommendation guys, hopefully it is simply a die issue that resolves this.

[bazineta]

Out of curiosity, how do you guys set up your FL resizing dies? For pistols I normally bring the ram up, screw the die down until it touches the shell holder, then go another 1/8th to a quarter turn down. I've done the same for rifles and am wondering if the last step is causing the brass to be slightly undersized like y'all are saying.

There are a lot of stacked tolerances involved, so it's really going to vary with your equipment.

I can say that in my setup, Redding dies and a T-7 press, when I set up the sizing die to cam-over, it'll size to 6 thousandths under SAMMI minimum.

Since I want it to be at cam-over, I use the Redding shell holder set that allows you to adjust that away; I use the holder that's 6 thousandths deeper than normal, and headspace ends up right where I want it (typically, I'm loading for semi-autos, so I just want SAMMI minimum, on a bolt gun, this would be a different story).

There are other manufacturers like PMA that make die micro-adjusters to get things dialed in just so, but then you're actually backing the die out a bit, so that wouldn't be the cam-over situation I'm looking for.

If you don't have a way to measure headspace easily, I'd recommend either the RCBS headspace gauge (easy to use, less expensive) or the Redding Instant Indicator die (extremely easy to use, absolutely great tool, more expensive).