6.5 cm lapua brass- ever seen this?

[Schnyd112]

This brass has been shot 10-12 times. I started seeing the marks in the first picture, it was 1 piece of 50. Then I got 12 more the next time I loaded them so I sectioned a piece I could see damage on and I sectioned a piece that was shot twice and scrapped because I trimmed it too short.

Have you ever seen brass dish out like this? Any guesses on causes?

This whole lot of brass has been scrapped now, I still have it but it's in the recycle pile. It looks like it is ready to separate if I shoot it again.

 

[Schnyd112]

Posted the wrong second picture.

 

[Barrelnut]

That's pretty common with brass that has been excessively sized. When you FL size brass and set the die up (as per makers instructions) the brass is pretty much sized back to SAAMI specs. This squeezes the brass and causes the braas to flow forward toward the neck. This is what causes the neck to grow. If you keep over sizing the brass this way, you end up with cases that look like the above. Have to be careful as they can separate in the chamber, when being fired. This is known as "case head separation". It can leave the forward part of the case in the chamber on extraction and allow hot gas to exit the rear of the chamber.

Lots of info on setting up reloading dies to only set the case shoulders back about 2 thousands when FL resizing. This way they fit the camber of the rifle they were fired in better and stop the excessive brass flow. They will usually only fit back in the rifle chamber they were fired in though.

Couple guys have some good diagrams of the phenomenon. They will probably post soon.

 

[Schnyd112]

I just don't see the excessive sizing in my operation. This brass measured 1.533" base to shoulder datum with a hornady comparator, virgin, unfired. Fired they measured between 1.537-.538. I then sized them back to 1.534". Every time. And they are done 100 at a time so I am not changing my die setup partway through.

I know it looks like a headspace issue but I have reloaded 1000's of rounds and have never seen this.

Also, this brass was growing .005-.010 in overall length from one firing to the next. Shoulders always were between 1.537-.538 fired. I would size to 1.534" at the shoulder, trim to 1.915 and have some cases that were 1.925" after firing.

 

[Barrelnut]

Well could be a loose (fat) chamber with tight (slim) dies and that is causing the brass to flow more than usual. The problem is definitely brass flowing from that are when the brass is sized.

Seems .005- .010 growth is a little much. My Lapua CM brass takes about three sizings to grow that much. I am using bushing dies and the expander does pull much on the neck though.

 

[Schnyd112]

Interesting theory. That may account for it, I always thought this die felt overly tight.

I agree on th growth. And it didn't do that until the brass had 8+ firings. Was more normal at .002-.003 pet firing.

 

[westcliffe01]

The rifle chamber is too long so the brass is stretched every time it is fired. Then in the sizing die, it is smashed down short again and the material flows into the neck and gets trimmed off. This results in the base wall getting thinner and thinner as you have seen. You can resolve the problem by changing the depth to which you run the full length die so that the shoulder is only bumped back 1 or 2 thousandths instead of the current 10 or more with every re-sizing.

I neck size my brass in a collet die and do no full length sizing and after perhaps 3-4 firings I may need to run it in a body sizing die (does not size the neck) until it can be chambered comfortably again, it will tend to get tighter and tighter to chamber as the cartridge tends to a "perfect" fit in the chamber, not allowing for any concentricity issues or the slightest bit of contamination...

The reasons why most rifles have a "generous " headspace clearance is to accommodate people who never reload and exclusively buy factory ammo which can have a lot of tolerance on the length. All this ammo needs to chamber reliably, but it is fired only once. For the most extreme case, imagine belted ammo for a machine gun. The weapon can chew through thousands of rounds and reliability is what is important, the state of the brass after firing is irrelevant so long as the cases do not separate. If you reload exclusively and only shoot the ammo in 1 chamber, you can run a much closer fit of the cartridge to the chamber than what is based on cartridge standards, so long as it runs reliably for you.

Things like seating the bullets far out and jamming them into the rifling when chambering may theoretically sound great unless you hunt and have to unload a chambered round and end up with the bullet stuck in the throat, powder all over the inside of the action and be messing around with a cleaning rod trying to push the bullet out while not damaging the lapped bore.... If you don't notice that you left the bullet stuck, that could of course result in a very bad day indeed if you chamber another behind it (assuming you are successful) and set it off.... I haven't done it, but I have come close till I figured out what was going on.... Needless to say I don't do that anymore...

 

[Ckgworks]

Interesting theory. That may account for it, I always thought this die felt overly tight.

Just curious.......what dies are you using? I have seen this with what barrelnut said, but I have some Hornady dies, I'm phasing out due to what I feel is excessive sizing.

 

[Schnyd112]

Just curious.......what dies are you using? I have seen this with what barrelnut said, but I have some Hornady dies, I'm phasing out due to what I feel is excessive sizing.

Forster benchrest dies. Used them on my .260 and they were great. This one seems like it takes a good amount of pressure and the sizing ball collects a lot of brass. Have never been really impressed with this set but the rifle is shooting killer groups.

It's a custom rifle built from a hawk hill blank.

 

[newmexkid]

Would it have anything to do with "hot" loads?

 

[nmbarta]

typically laupa brass has strong primer pockets.
Brass is eventually going to fail. Case head separation and/or loose primer pockets are the most common. At 10-12 firings, it's just done.
Nothing wrong with that imo. As mentioned above, over sizing is a great way to end up with early case head separation.

 

[Schnyd112]

Would it have anything to do with "hot" loads?

The first 3-4 firings were with RL 26 and while I wasn't seeing pressure signs, 2900 FPS with 140's out of a creedmoor has got to be high pressure.

typically laupa brass has strong primer pockets.
Brass is eventually going to fail. Case head separation and/or loose primer pockets are the most common. At 10-12 firings, it's just done.
Nothing wrong with that imo. As mentioned above, over sizing is a great way to end up with early case head separation.

So this was my thought. Then I have a buddy that sliced a 6.5x47 lapua case that had been shot a dozen times and the primer pocket opened up, result shows nothing like what I have. It may just be the creedmoor fails in that spot, the x47 is at the primer pockets.

So I started questioning my theory and I posted this to see if anybody else had seen it. I am not complaining, 1000 rounds of high quality brass for $100 is an investment I am alright with, just curious.

 

[MagnumManiac]

There is ONE, AND ONLY ONE cause for incipient case head separation and that is excessive headspace from a gun problem or induced by over sizing the brass.
High pressure loads do not cause this, trimming the brass is caused by this excessive brass working, nothing else.

I try not to move my brass cases more than .0015" in ANY direction, including the case body, not just the shoulder.

I bet if you reduce the amount you are sizing AND remove the expander from your die, I would suggest having Forster measure your die neck and measuring your LOADED brass and get the neck honed to .0015"-.002" under loaded round spec, I bet if you have this done your problem will go away.
Expanders can drag the shoulder forward, then you adjust the die to compensate, then the brass hardens and resists the sizing, causing excess headspace without you realising it.

Cheers

 

[Hondo64d]

Forster benchrest dies. Used them on my .260 and they were great. This one seems like it takes a good amount of pressure and the sizing ball collects a lot of brass. Have never been really impressed with this set but the rifle is shooting killer groups.

It's a custom rifle built from a hawk hill blank.

My last two sets of Forster dies have narrowed the case at the shoulder quite a bit, from fired dimensions, .005". This is significantly more than my Redding body dies do. I'm wondering if that might have the same effect as pushing the shoulder back too much.

John