Head Space

[mooretitan]

Trying to figure out some case separation. Lapua brass, 4th reload, 260 Remington, under max pressure. I was checking brass today and notice a slight ring around the base of the brass. Roughly 10%. I ran the go and no go again on my savage and everything work. Go gauge went and no go gauge bolt would not close.
I have never had case separation issues before and have reloaded a lot.
Any help???
Thanks

 

[2muchhp]

Have you measured the brass before and after shooting to known how much it is moving?

 

[49ereric]

Don’t bump the shoulder back until absolutely needed and then a minimum.
my M1917 06 would do the same thing case head separations @3 reloads so I went to neck sizing only. Brass has grown but fired cases still chamber fine.
they won’t chamber in a different 06 though.

 

[2muchhp]

In a nutshell the brass has to be moving.
If your full length sizing and your chamber is on the high side of the tolerance its going to stretch more
It would be good to know how much the shoulder is moving from first fire, second and third.

 

[eod.tek]

That may not be case head separation. I have a 300 Norma that I use Lapua brass in, and have a very similar line that develops right at the bottom of where my sizing die ends. When I first saw it I was terrified because Lapua brass impossible to find for the Norma right now. But I cleaned some, and both ran a paper clip along the inside edge to see if it caught and put a bore scope on the inside of the cases and they looked perfect. 3x more loads later and no failure.
Not saying it's not separation because it may be, but I would clean and inspect the inside of your brass, maybe even band saw one open to look before condemning it all. And if you end up using it again, keep close measurements of growth, because it'll be your best indicator

 

[rayporter]

run the paper clip in like or cut one open. the die can leave a mark and the box you carry them in can leave a ring, too.
get the tools to measure shoulder bump.. you have to know how much you bump.

 

[mooretitan]

I need to do a little better on measuring after each firing. I ordered some gauges and will do a better job keeping records.
I will cut a few open and see whats going on. I am sure its not just a ring from the die or box. I can actually catch the dent of the line when I run my nail over the brass.

Just ticks me off a little that I did not pay better attention to the small details of measuring the stretch and bumping the space back correctly

 

[Vern400]

There is no need generally to push a shoulder back more than a few thousandths. In fact I only neck sized 308 for years but eventually a slight headspace interference comes with that.

I've seen the light with neck turning as needed, and bumping shoulders to a thousandth or two headspace clearance.. it's a level more advanced than starting out.

If you started reloading by setting your resizing die against the shell holder, and jamming that sucker home, then I'm going to say it's not a surprise and yes you should look for signs of separation and thin case while near the head.

BUT you should confirm. I get bright rings regularly and I know I'm pushing my RL15 loads. The hotter I make them, the better they group. But they're safe, not over published charge. I've gotten 5 or 6 loads on RP brass and the failure mode is mostly neck splits, even with annealing.