Re: 25-06 case head seperation?
Bounty Hunter wrote:
You are "assuming" that the die screwed down until it touches the shellholder actually matches your chamber. That is the first mistake!
Like Bart said, you either have to use some type of precison mike or bump gauge to measure your fired cases on the shoulder. From that you only want to bump back .0015-.002.
Many times you can screw the die all the way down and get .015 or more push back which will lead to case head separation.
There are variances in shell holder heights, dies and such that you cannot just screw the dies down, resize and expect long case life.
I have also seen dies that had to have .020 ground off the bottom of the die to get proper sizing.
FL sizing is sizing the body AND moving the shoulder back some, the only question is how far pushing it back.
Different mftr of the dies have different thread pitchs and a 1/4 turn does not equal a quarter turn with the next die.
Get in the habit of measuring the shoulder, starting high of the shoulder and coming down very little at a time until you get the no more than .002 shoulder push. Forget the mftrs instructions, they are not designed for long brass life.
I agree with nearly all of what you wrote. I've not seen dies that were way too short, but I guess they could happen. I have seen chambers that are too long.
I do all the measuring you suggest and then some, and since I chamber most of my own rifles I also use go and no-go gages to check chambers.
I use a feeler gage spacing between the top of the shell holder and the bottom of the die to get small changes, trying to do it with fractions of a turn is too coarse an adjustment, which is really the important point.
I have a '53 Model 70 .30-06 that stretches brass even though I don't bump the shoulders more than .002" +/- .001". 5 reloads results in about .007" of dip reading in wall thickness just above the base using the RCBS case master gage, and I pitch the brass. I need to trim the brass after every other firing. The chamber in that rifle is really rough (as seen in a borescope exam). I'ts going to get a dose of oil soaked emery paper after I do one more range trip with it. I like to do one thing at a time and I just finished pillar bedding it. I think getting that chamber to nice 320 to 400 grit cross hatch will do it a lot of good. At the moment it scars the brass.