First Case Head Seperation

[RRP II]

Case is a Hornady 6.5 Creedmoor that had been loaded six or seven times. Case was full length resized with a bushing die after annealing. Case was loaded with H4350 to 42.4 gr. and a 140 Berger VLD. Round was shot from my bolt gun with ammo that shot well before this incident and I fired 10 round after this round without issue. The other case in the photo is from the same lot of brass that has been loaded 6-7 times. Is this a case of just to many reloads or is something else going on here that I am not aware of or don't see?

 

[427Cobra]

Case head separation is directly caused by over bumping shoulders, I have 260 Rem(Win 243/7-08) brass that has over 30 loads, and now some 6.5 Creed that has more than 10 firings

 

[oldfudd]

I'm trying to learn something here. What is causing the indentations just below the shoulder in the picture of the case with the separated head? I've only seen this before where too much lubrication was used when sizing the case. I'm assuming it isn't the issue here ? ? ?

 

[roggom]

The indentations are an indicator that the pressure inside the case was lower than the pressure outside the case, even for a micro second. The gas is supposed to stay in the case, expanding it against the chamber walls, then pushing the bullet through the barrel. In this situation, the gas was pushing the bullet, but also escaping into the chamber. Just think about your shampoo bottles when you travel from high back down to sea level. You open them at high altitude and there is an equal pressure inside and out. Take them down and the pressure is greater outside than inside.

You also get this when you use a slow powder and grossly underload the charge.

OP, I would take one of the 6-7 fired cases and split it down the middle and take a peek. Check for a wear ring right about the spot where your case separated. I agree with the above post that bumping the shoulder too much can be a culprit(I have done this).

 

[oldfudd]

roggom -- thank you. Are you saying that because of the case head separation, that the pressure of the burning powder was allowed to escape from inside the cartridge and instead build up in the chamber itself, thus allowing the pressure inside the ruptured case to be less than the outside chamber pressure? This is assuming that there wasn't an underloaded charge (as described by you above).

 

[OF&B]

What are the diameters of sized and unsized cases at the failure point?

 

[AIdog]

check wall thickness with rcbs case master gauge.... and double check how much ur bumping back the shoulder when u FL size, should only be -.0015" thats all that is needed

 

[Kiba]

Case head separation is directly caused by over bumping shoulders, I have 260 Rem(Win 243/7-08) brass that has over 30 loads, and now some 6.5 Creed that has more than 10 firings

While oversizing is often a primary cause, crappy brass is a problem too and you can have a head separation even if you are not loading too hot or over sizing. I experienced a case head separation with FGMM 308 brass after 7 loads; brass was FL sized every time bumping the shoulder back 0.001" and the load was nowhere near hot. After the one failure I sectioned a few more cases from that batch with the same amount of loads and they were all very thin right above the web and close to failure. Then again, FGMM brass is known to be very soft and the primer pockets on that batch of brass were done anyways. That shouldn't be the case here though as while Hornady brass isn't the best on the market it is pretty good overall and certainly isn't as soft as FGMM.

OP, your load doesn't sound excessively hot but I would question how far you're bumping the shoulders back every time you FL size. For that batch of brass that the failed case came from I would do the "paperclip test" at the very least and even better I'd section a few cases and have a closer look just above the case web in the area the pictured case failed.

 

[BuzzBoss915]

Case head separation should be a very rare occurrence. It seems to be a rather common thing with relatively new handloaders. Did the case fall out or did it require a lot of effort?

I expect, you would be better served by dumping the rest of this lot of brass before it causes more trouble. Generally speaking, the procedures that caused one rupture will cause incipient separation and you need to check for it as described above or the paper clip method. Hate to deal in generalities but this is almost always "pilot error" unfortunately. If the factory, or your gunsmith is responsible, you would see a problem almost right away, not on the sixth reload. Same opinion regarding poor quality brass.

As someone said, getting a high number of reloads should be the rule, not the exception, I easily get 20, never have to retire a lot of cases at 6 or 7, but part of the secret is to keep your pressures moderate. BB

 

[RRP II]

Case head separation should be a very rare occurrence. It seems to be a rather common thing with relatively new handloaders. Did the case fall out or did it require a lot of effort?

The case head dropped out when bolt was retracted and the mag. removed. The top part of the case was removed via running a bore snake.

I wii cut some of cases open to see if this is a larger issue with this group of brass.