Case Failure. Advice Please

[Hawk in WY]

I have lost cases due to split necks before but never this.

.300 Win Mag loaded near max.

Near case head separation, obvious crack just above belt, but with major dimples just below the shoulder every ninety degrees around the case.

Winchester brass.

Four times fired. Annealed in an AMP Annealer after three.

All other cases in the lot look fine. Pass the paper clip test.

I suppose four times is not unusual for .300 WM, but brass is expensive. Around 200 in this lot.

Scrap the lot or keep reloading?

 

[trophyhunter]

During each of these sizings how much are you bumping the shoulders ?

How tight is the chamber ?

Have you sized the area just about the belt with a body sizing die ?


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[vh20]

Odd/suspicious that it happened on first firing after annealing, and shoulder is collapsing? Got pics?

 

[RampedRaptor]

During each of these sizings how much are you bumping the shoulders ?

How tight is the chamber ?

Have you sized the area just about the belt with a body sizing die ?


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This is exactly where I would say to investigate first also.

 

[Statusquo]

Welcome to the world of belted cases.

Inspect the lot. Use a paper clip to feel inside the case for a groove. A close visual inspection usually is enough for me. Sort them based on severity. Chuck the bad ones. It should be obvious. This is where keeping cases organized helps. Dont mix twice fired brass with 4x fired brass, etc


I have a series of cases that shows the progression of case head separation. I'll try to upload a pic tonight.

Are you full length resizing? This speeds up case head separation and 4 loadings is reasonable to expect.

The dimples is what happens with case head separation.

 

[shoot4fun]

The best thing to hit the market for loading the 300WM, or any belted for that matter, is the Innovative Technologies sizing die. The problem with 300WM is that you either size all the way down to the belt and risk pushing the shoulder back way too far (resulting in case separations) or you drive yourself batty dealing with inconsistent base to datum measurements. Your FL sizing die most likely just can't do an ideal job on both tasks.
I have 300 WM brass loaded 10 times using this die and it is still ready for more. Not shooting wimpy loads either; 230 Hybrids with a lot of Retumbo.
BTW, I don't think annealing has anything to do with what is happening.

 

[Hawk in WY]

Correction: Brass is Hornaday not Winchester.

Using full length resizing die to bump the shoulders two to four thousands.

I set up the die to bump the shoulder two thousands from the shortest fired case in the lot. They vary by around two thou.

I keep brass in separate lots. If some are twice fired they go in a separate box from three times fired until the first lot catches up.

Krieger barrel. No idea how tight the chamber might be.

I'm using a Forster full length resizing die. but obviously not full length body sizing the way I'm setting it up.

No idea how to upload photos, but sounds like the dimples are normal with a case head separation. Shoulder is not collapsing. Dimples are just below shoulder.

I will check each piece again and investigate the Innovative Technology die. Any other full length body sizing die which will play well with a two thou shoulder bump?

I have run a test with .270 Remington brass on brass life also shoulder bumping two thou. Gave up after they were still going strong after 12 reloads.

I expected less with .300 WM, but was hoping for more than four..

 

[Sheldon N]

Correction: Brass is Hornaday not Winchester.

Using full length resizing die to bump the shoulders two to four thousands.

I set up the die to bump the shoulder two thousands from the shortest fired case in the lot. They vary by around two thou.

Did you check the shoulder bump on the annealed brass after setting it up originally? Annealed brass can result in way more shoulder bump than regular brass, even at the same die settings.

I've lost cases to that exact situation before... Changed annealing, kept the old die settings and didn't double check shoulders, got too much shoulder bump... case head separation.

 

[Hawk in WY]

Bingo!

Sheldon may have nailed it.

Less spring back with annealed brass.

Can't imagine this would cause that much difference but that may be the answer.

I will check shoulder datum when I resize next round.

Thank you all for your analysis and advice.

 

[Sheldon N]

Yeah, it was a painful lesson for me. Lost about 100 cases of Lapua brass that would have otherwise gone on much much longer.

 

[Supersubes]

You may not be running the case as deep as you possibly can into the die, but you ARE full length sizing.

What kind of rifle is this? I dont use the size of fired cases as a basis for bump, because they vary, and dont perfectly represent chamber size. I check for fit in the chamber. For example: Take the stiker assembly out of the bolt and test fit sized cases until the bilt closes with no resistance, but wont allow you to thrust the bolt forward(headspace). When you've found that case, measure it. That is zero headspace. Then set the die to your desired bump, like .002 shorter than the "0" headspace case. Simply using the shortest case isnt a good reference, because it might need no bump at all. What sheldon said about annealed cases sizing differently is spot on. Same could be said for changing lubes, changing brass makes or lots, or die cleanliness.

 

[Sheldon N]

I dont use the size of fired cases as a basis for bump, because they vary, and dont perfectly represent chamber size. I check for fit in the chamber. For example: Take the stiker assembly out of the bolt and test fit sized cases until the bilt closes with no resistance, but wont allow you to thrust the bolt forward(headspace). When you've found that case, measure it. That is zero headspace. Then set the die to your desired bump, like .002 shorter than the "0" headspace case.

One caution about that approach is that you're relying on your sizing die dimensions matching your chamber. Imagine if your sizing die was not very good at sizing the base of the case but was fully engaging the shoulders. You might not be able to easily chamber that brass until you'd already bumped the shoulder a few thou, which would then give you erroneous measurements of shoulder bump needed.

Probably the more accurate way to measure the chamber is to measure brass that's been fired a couple times, ideally with full power loads. Then look for the longest/largest dimensions and that's a close indicator of the chamber size. The basic premise being that it's not possible for the case to be any bigger than the chamber itself.

Then when sizing pay attention to base diameter, shoulder diameter, and shoulder datum length to make sure the whole case is being appropriately sized. You can then combine that in conjunction with the stripped bolt to feel when it will chamber easily with no effort. My experience is that if the whole case is being sized properly you'll get a zero effort bolt close around 1.5 - 2 thou of shoulder bump. I target that number for my sized cases since i want as little sizing as possible. If you added 2 more thou of shoulder bump on that number you'd be bumping close to 3.5 - 4 thou from the chamber size and this could contribute to premature shortening of case life.

Anyhow... sorry for the rabbit trail/digression.

 

[Hawk in WY]

In response to what kind of rifle is this, it's a Defiance action, Krieger barrel, McMillan carbon fibre stock, extremely light, 6.5 pounds rifle only, custom hunting rifle.

Holds 0.5 moa groups to 500 yards. 200 gr Barnes LRX with Reloder 26. Built as an elk hunting rifle.

My conclusion from this discussion is I need the Innovation Technology die and bump .002 from the longest, not shortest fired case. Will try that with the stripped bolt.

Many thanks for all the good thoughts.

 

[FLIGHT762]

It's been my experience after annealing, the case shoulders will get bumped back .004"+ more than un annealed cases with the F/L die set at the regular -.001"-.002" bump . I use my Redding competition shell holders to adjust to get less shoulder bump on freshly annealed cases. Check and see if that's the case.

I purchased the Innovative Technologies F/L die but found I haven't needed to use it very often. I don't reload a lot of belted magnums, just a few rounds now and then for hunting.

 

[Supersubes]

One caution about that approach is that you're relying on your sizing die dimensions matching your chamber. Imagine if your sizing die was not very good at sizing the base of the case but was fully engaging the shoulders. You might not be able to easily chamber that brass until you'd already bumped the shoulder a few thou, which would then give you erroneous measurements of shoulder bump needed.

Probably the more accurate way to measure the chamber is to measure brass that's been fired a couple times, ideally with full power loads. Then look for the longest/largest dimensions and that's a close indicator of the chamber size. The basic premise being that it's not possible for the case to be any bigger than the chamber itself.

Then when sizing pay attention to base diameter, shoulder diameter, and shoulder datum length to make sure the whole case is being appropriately sized. You can then combine that in conjunction with the stripped bolt to feel when it will chamber easily with no effort. My experience is that if the whole case is being sized properly you'll get a zero effort bolt close around 1.5 - 2 thou of shoulder bump. I target that number for my sized cases since i want as little sizing as possible. If you added 2 more thou of shoulder bump on that number you'd be bumping close to 3.5 - 4 thou from the chamber size and this could contribute to premature shortening of case life.

Anyhow... sorry for the rabbit trail/digression.

Im a super anal case measurer, so i typically put a value on everything, including after sizing diameters, as well as headspace. I have multiple FL dies in the same cartridges for almost everything, because i wasnt happy at some point with some chamber, how they played together. But that all just comes back to fit. I knock the primers out of the fired test cases and start measuring, and continue measuring as i work the dies down until i find a zero headspace fit, then go from there. I think .001 is plenty, but since i use redding comp shellholders a bunch, i have to work it .002's. Usually i dont end up a full .002 under though.

Your mistaken though on fired brass size. It will absolutely grow larger than the static chamber size. We know this simply because that brass eventually wont fit. Whether thats done with a proof round, or by a neck size only loader shooting a case over and over without sizing the body. Chamber pressure grows the chamber, and thrusts the bolt. Its that same radial expansion which is measured by a strain gauge, for pressure test measurements. I recall dan lilja doing one of his receiver evaluation articles years back. He tested the remmy 700 and .338 lapua, when that was a common topic. Based on the dimensions and metallurgy, I seem to recall that the lugs flexed .012" or somewhere in that range. Thats from memory, but even if it's half that, thats a lot of movement! My AXMC .338 does this with lapua brass. I documented it in my lapua V. Peterson brass test in this section. Lapua brass, even at normal pressures (250's at 2900-2950), comes out .001 longer than chamber size on the first firing.

 

[Supersubes]

I was wrong. It was a 378 weatherby in a remmy 700, the the thrust forces flexed .0026".

http://riflebarrels.com/378-weatherby-cases-in-the-remington-700-action/

 

[Sheldon N]

Dang, even a couple thou is a lot of flex, though that was with a bit of a monster round. I'd have to imagine for more normal size cartridges the numbers are smaller. Most of what I'm shooting is smaller caliber with loads that are not capable of stretching the chamber in the same fashion. Fired cases rechamber without much difficulty just a bit of light effort on bolt close. I guess we're both going for the same ultimate target... accurate brass to chamber fit and keeping any excess headspace minimized.

 

[Supersubes]

Certainly, less area to work in the smaller case means less expansion. One more reason that FL sizing is the only way to fly. Just sucks up that little intricacy.