Cause of case separation ??

[Bob C]

Today I fired 19 rounds of 30/30 reloads in my 14" Contender.  The brass was all once fired, and from factory ammo. Some R-P, some W/W.

My load was 24.0 IMR 4198 with a 150 Sierra BTSP. I set the sizer by screwing it in a little at a time until the action closed easily on the re-sized case.

The first six rounds were in W/W brass, and did fine. The seventh round was R-P, and I got a complete separation .66" above the base of the rim.

I fired the rest of the rounds without any separations, but most of the empties have a bright line at the same place where the one round separated. It's present on the W/W brass, but less so than on the R/P brass.

I miked the fired brass at the shiny line, and it was all .416".  Unfired brass at that same point is .411".   At the base the fired brass is .420", and at the base of the shoulder it's .407".  I also fired 25 or so factory rounds today, and many of them also show the bright ring at that same place, and they have the same dimensions after firing.

The most likely possibility I can think of are an oversized chamber,  Since it's occurring with factory loads, and with brass from two different makers, I doubt if it's a badly adjusted sizer, or bad brass.

Any comments or suggestions will be appreciated.

[RonF]

Take a piece of fairly fine wire, like picture hanging wire, maybe .025-.035" diameter, and make a right angle bend about 1/4" from the end.  Use this to feel the inside of the case.  If you feel a notch or groove where those bright rings are, then your cases are stretching due to too much headspace.  I don't know what the cause may be, but I'd check to make sure the lock-up is secure and maybe install new locking bolts.  If you're convinced the chamber is too long, send the barrel in to T/C.

For your handloads, you can make sure the sizer die is set long.  You can use new brass and make it fit by running it over an 8mm expander button and then resize so you get a secondary shoulder at the proper location to headspace, then only resize to the fireformed shoulder.  This will prevent stretching on the first firing.  I once had a barrel in .256 Win that gave short brass life, so I fireformed using lighter loads and was careful to only partially size the case.  Seemed to work.

Good luck.

RonF

[BCB]

Bob C.

I had a TCR 87 single shot rifle that had a headspace problem.  It would seperate the brass on the first firing and at the most on the 2nd firing.  (Maybe that's why this rifle isn't made anymore!)

Regardless, get a gunsmith, or maybe even the place you purchased it, to us a "go-no go" headspace gauge.  That will at least let you know if there is a headspace problem with the actual chamber.  Good-luck...BCB

[KYODE]

only size down until the die just meets the neck shoulder junction, or is just minutely short of it. you can see on the neck how close it is. i've been using feeler gauges to set my dies off the shellholder. that way i can adjust if a problem comes up.
i don't really understand your sizing until the case goes in freely :?  a fired case should still chamber easily after firing, and before sizing. if you sized till the die bottomed out on the shellholder, maybe you shoved the shoulder back to far :?
keep us informed of your findings. a paper clip, bent with a short 90* angle, is good to reach inside the case and feel the case walls. you can feel the crack inside before a separation, like ronf says.
i've only had one case separation, and it was my fault for pushing the shoulder back too far.  

[Bob C]

Checking the inside of each case for a "fault" line with a bent paper clip showed that none of the once fired brass has a problem, but that three of eighteen of the twice fired do.

I'm going to discard the cases where there seems to be a problem, and then proceed with my loading. I'll ckeck the brass regularly, and make very sure I'm not setting the shoulder back at all.

Thanks for the replies.

[PaulS]

I feel the need to ask a question.... do the factory once fired rounds fit in the gun and allow it to close and fire? If so have you tried just partial sizing so that the first half of the neck is resized?
Even an oversized chamber will not cause case head separation that quickly - normally it takes three shots at least. Remember that the contender must headspace on the shoulder - even with rimmed cartridges.

Your problem sounds like a headspacing error caused by a combination of full length sizing of the brass (setting the shoulder back) and a long chamber (in effect fire-forming the brass with each shot and then putting it back to factory spec with each loading) Like taking an Ackley Improved cartridge and sizing it in a "regular" die then firing in the improved chamber again.

PaulS

[Bob C]

Thanks for the very helpful replies.

Yesterday I resized 16 rounds of once fired W/W brass from factory loads fired in my gun with the die adjusted so that there was no contact on the last 1/8" of the neck above the shoulder.

All were loaded with the 150 Sierra BTSP and a load of IMR 3031 which was OK in all four manuals I checked.

There were no problems while firing htese rounds. There is a line at the same place on the outside of the brass, but checking the inside of the cases with a paper clip showed no apparent faults.

[Double D]

There are two thing you can do to increase the life of brass in Contenders. Especially high intensity rounds like the .223 and 30-30.

First index the rounds when they go in the chamber and second adjust your sizing die so it takes a crisp snap to close on a loaded round.