6 PPC case life

[CJ6]

Last night I loaded 30 rounds to try various neck tensions (.256, .257, .258). The load was 29.5 grs of VV 133 (ALL HAND WEIGHED) with 65 gr. SBTs .008 jam (my normal seating depth). I have 20 firings on this box of 50 cases, all sized with a "fitted" sizer. The sizing die has not been removed from the press since it was set up in 2009 (I clean it on the press). To the point here.....Today while testing 3 caseheads ruptured just above the .200 line. I had no indication of rupture at time of firing (no smoke or off impact shots). I noticed them while getting them cleaned and ready for next loading. Also while inspecting I found 11 more cases with the tell tale of near rupture (bright "ring") just above the .200 line. I checked the other box of 50 (empties) that would've
been loaded next (came from same Gold box Lapua) and I see NO issues internally or externally with them (they have 19 firings on them). I have NEVER seen this type of failure with brass. .....Open to answers and critizems.

 

[jimmymac]

How much shoulder bump?

 

[CJ6]

.002

 

[jimmymac]

Hmmm. Good there.

Have you had to trim the brass many times over the 20 firings?

 

[BoydAllen]

For my PPC, since I am always loading at the range, for a new barrel I will fire form a new case and fire it several times, neck sizing, and checking the shoulder to head length. I do this with a stout load, not concerning myself with tune or accuracy, something in the high 29s. When the case stops growing head to shoulder, I note that length and set my die to bump back .001 from that. IMO if you have been able to use the same die setting for that long it tells me that either you are bumping based on a case that was not tight head to shoulder, and bumping more than you intended, or are shooting untypically light loads, or perhaps both. The only time that I have seen a separation is when I have gotten sloppy with managing bump. Related to this is the difference in die setting I have seen for freshly formed vs. high milage cases. One time I switched from the well used to the freshly fired and instead of the .001 that the setting produced with the high use brass, I got .0035 with the fresh brass. This was due to the difference in spring back, with the high use brass being work hardened quite a bit compared to fresh brass. I keep my brass in sets that I fire and size in strict rotation, and those sets can vary quite a bit in work hardening, so going forward I reset my die at the beginning of every session, for the particular set I was working with. This approach has worked very well for me for years.

 

[CJ6]

3 times, but very minimal shavings after fully fire-formed (4 firings) and some no shavings.

 

[CJ6]

Boyd you may be on to something with the lighter loads. All but the last 3 loading on this batch of brass has been with 28.5-28.9 grs. These last 3 have been with 29.5-29.7 grs.

 

[BoydAllen]

One toy that I bought a couple of years ago is one of the micrometer style case gauges. The zero point corresponds to what a GO gauge measures. I can measure a tight case with it and I have a consistent reference point for that barrel. When I first used it I did an elaborate bump investigation for my newest barrel, using tape on the back of the case to artificially produce a case that was too tight for the bolt to close. With that in hand, I used my PMA Micro Die adjuster to carefully adjust the die so that I could place the bolt handle ( stripped bolt) anywhere within its vertical travel with almost almost zero force. Using that as a reference I set the die for .001 bump and the handle would fall freely. I then used the Whidden gauge to measure the case and recorded that in my notes. For this barrel a proper dies setting is .0015 longer than zero. I am not saying that you have to do anything this involved, but after all I had a new toy to play with. For those that want to try this approach, given that Whidden has discontinued this caliber, it is cheaper to shop around for a good deal on a go gauge and use it as a reference standard. In that case, assuming that the go gauge agreed with the zero on the gauge, my setting would be GO +.0015.

 

[Tim Singleton]

Whether you realize it you are over sizing them. That’s really the only thing that will cause this and about 20 firings is when it would show up

 

[Shooter13]

For my PPC, since I am always loading at the range, for a new barrel I will fire form a new case and fire it several times, neck sizing, and checking the shoulder to head length. I do this with a stout load, not concerning myself with tune or accuracy, something in the high 29s. When the case stops growing head to shoulder, I note that length and set my die to bump back .001 from that. IMO if you have been able to use the same die setting for that long it tells me that either you are bumping based on a case that was not tight head to shoulder, and bumping more than you intended, or are shooting untypically light loads, or perhaps both. The only time that I have seen a separation is when I have gotten sloppy with managing bump. Related to this is the difference in die setting I have seen for freshly formed vs. high milage cases. One time I switched from the well used to the freshly fired and instead of the .001 that the setting produced with the high use brass, I got .0035 with the fresh brass. This was due to the difference in spring back, with the high use brass being work hardened quite a bit compared to fresh brass. I keep my brass in sets that I fire and size in strict rotation, and those sets can vary quite a bit in work hardening, so going forward I reset my die at the beginning of every session, for the particular set I was working with. This approach has worked very well for me for years.

I'm not as meticulous as Boyd but regardless of what I'm shooting I check the cases before sizing and readjust die (if necessary) for that lot of brass.

 

[Field_2_Fork]

Were the cases that had the separation sized with the .257 bushing? Perhaps the increase in tension was all it took to up the pressure enough to push the worn brass over the limit?

 

[CJ6]

Were the cases that had the separation sized with the .257 bushing? Perhaps the increase in tension was all it took to up the pressure enough to push the worn brass over the limit?

My normal bushing is .256. I honestly don't know which bushing/s the separations occured with, as I didn't notice the issues until I was home.

 

[TRSR8]

Over bumping the shoulder is the likely culprit. Lots of ways to measure it wrong, the best method is the device with die body and dial indicator up top.
Can’t tell you how many of our club shooters swore they bumped .001“-.002” that turned out to be .003”-.005”.

 

[SKWERLZ]

How much initial growth upon first firing?

 

[AlNyhus]

The initial firing is a major player in this.

 

[INShooter]

The initial firing is a major player in this.

How so please?

 

[JMayo]

I've shot them until the pocket is loose. 1200 + bullets, 200 cases. None ever separated.
N133 28.9

 

[searcher]

It took me a long time to find the "right" way to bump shoulders - and that is to first determine when it is actually needed - and by how much. When running a new set of brass, I jam the bullets to blow the shoulder out as much as possible. Some will argue that the shoulder will eventually blow forward - but regardless, one needs to know when they are fully forward. Because it can take several firings (or never on light loads) to fully blow forward, I'd rather save my barrel and get my rifle tuned in the fewest number of rounds as possible. Others use hydraulic methods to blow the shoulder out - others corn cob media - others a "slave" barrel cut with the same reamer by a competent gunsmith who is capable of getting the chamber within a few .000 (which is about as good as it gets) to save round count on the match barrel.

So - after the brass has been fired, I body size only, then chamber the brass and if there is not the slightest hint of resistance when closing the bolt, I do not bump the shoulder AT ALL. This will be repeated after subsequent firings until slight bolt resistance is acknowledged. THEN I bump .001". But if I'm loading for a match, I chamber every case and only bump those actually needing it - as they all won't need it. They never, as you know, grow the same length in the same number of firings. If you are quick to get your shoulders fully extended and monitor your cases in this manner - your case life will be extended for the longest life your load allows for. That gets me 50+ loadings and I'm not pushing the velocity envelope to the extremes some do.

It is interesting that one box (from the same batch, with approximate same number of firings) exhibits case separation and the other box shows no signs. A number of things can cause this - such as annealing one box and not the other as much, firing a different load in the other box - such as a lighter or heavier bullet, not turning the necks enough on as tight neck chamber on the ones you are having trouble with, allowing the overall trim length to be exceeded on the box you are having problems with, etc. And that is all the while assuming you didn't set the shoulders back a tad more on the problematic ones. Lots of variables - and usually a combination of very minute things working together.

 

[CJ6]

I've shot them until the pocket is loose. 1200 + bullets, 200 cases. None ever separated.
N133 28.9

My "normal loads" were between 28.5-28.9. never any issues. I bumped up to 29.5-29.7 on the last 3 firings. Total rounds at the 29.5-29.7 is 250 but they have been fired a total of 20 times (1 box of 100). The last 50 have been loaded 19 times . BTW the pockets are still tight.

 

[CJ6]

It took me a long time to find the "right" way to bump shoulders - and that is to first determine when it is actually needed - and by how much. When running a new set of brass, I jam the bullets to blow the shoulder out as much as possible. Some will argue that the shoulder will eventually blow forward - but regardless, one needs to know when they are fully forward. Because it can take several firings (or never on light loads) to fully blow forward, I'd rather save my barrel and get my rifle tuned in the fewest number of rounds as possible. Others use hydraulic methods to blow the shoulder out - others corn cob media - others a "slave" barrel cut with the same reamer by a competent gunsmith who is capable of getting the chamber within a few .000 (which is about as good as it gets) to save round count on the match barrel.

So - after the brass has been fired, I body size only, then chamber the brass and if there is not the slightest hint of resistance when closing the bolt, I do not bump the shoulder AT ALL. This will be repeated after subsequent firings until slight bolt resistance is acknowledged. THEN I bump .001". But if I'm loading for a match, I chamber every case and only bump those actually needing it - as they all won't need it. They never, as you know, grow the same length in the same number of firings. If you are quick to get your shoulders fully extended and monitor your cases in this manner - your case life will be extended for the longest life your load allows for. That gets me 50+ loadings and I'm not pushing the velocity envelope to the extremes some do.

It is interesting that one box (from the same batch, with approximate same number of firings) exhibits case separation and the other box shows no signs. A number of things can cause this - such as annealing one box and not the other as much, firing a different load in the other box - such as a lighter or heavier bullet, not turning the necks enough on as tight neck chamber on the ones you are having trouble with, allowing the overall trim length to be exceeded on the box you are having problems with, etc. And that is all the while assuming you didn't set the shoulders back a tad more on the problematic ones. Lots of variables - and usually a combination of very minute things working together.
I have not loaded the other 50 yet (they have 19 firings on them) 2 at 29.5-29.7) 1 firing at each powder charge. and this is on my mind...Should I revert back to the 28.5-28.9 charges too see if the charge weight is the issue. It does shoot more consistent at the higher 29.5-29.7 charges.