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Discussion in 'Reloading' started by jmason, Jun 22, 2009.
How do I determine when my brass has exceeded it's useful life before I have case head separation?
Case head separation is a sign of improperly adjusted FL size dies and can happen in as little as 3-4 firings.
IF your dies are adjusted correctly to give .002 bump on the shoulders, case head separation will not be an issue.
As for the usefull life, you will see other signs depending on the pressure you are running and overall softness of the brass. Primer pockets will loosen and necks will work harden are the two most common.
Necks can be reannealled to lengthen life and less pressure will keep primer pockets intact.
I have run cases as many as 30x and Tom Sarver who set the IBS LG world record group at 1k with a 1.4xx inch group, 5x and 50 score had 54 reloadings on his cases at the time of the record and retired them at 80 reloadings (Lapua brass) and annealed after every shot.
BH- I do anneal after 2-3 firings. I'm using Winchester brass. I'm on the tenth firing for the brass and all seems well. I just wondered if there was a way to measure the case wall near the base? If there is a method, how thin is too thin?
I think this is what you are talking about . Jim
OK, you can use a dental pic or bent wire and feel inside to see if you have any grooves where a separation might occur. However, if you do it is caused by improper sizing. Fix that first.
If the FL sizing is correct, there is no "thinning" of the walls.
Jim- that link isn't working for me was it for the RCBS casemaster gauging tool?
BH- If there is no thinning of the walls how do you conclude it no longer useful. It can't last forever. Does it just get to the point you can't anneal it? (it won't become flexible anymore)
I'm probably not FL sizing right anyway. More often than not after I anneal and size I find my case necks have stretched out and need trimmed to be uniform again.
I don't believe FL sizing will correct thinning in the body..
For one, shoulder bumping doesn't shorten anything below the shoulder.
And second, sizing the body inward will not thicken the wall where it has stretched, anymore than elsewhere(so it's still the weak link).
I think it's a good idea to monitor it if your loosing brass(trimming). That brass came from somewhere, which came from somewhere, yadda, yadda.
I also think the only ways to address it, is to toss after so many firings, or prevent it to begin with.
There is a misconception that FL dies take everything back to a 'standard'. This is not true at all.
FL dies, like any other, simply squeeze brass where there is an interference fit.
There are so many things that affect that fit and take...
yes # 87310 case master gauging tool . Jim
There's no need to toss your cases early, and there's no reason to EVER get a headspace separation. You should measure your handloads (when you setup your dies) to see how much chamber clearance YOUR handloads will have (at the shoulder) in YOUR particular chamber.
Bumping the shoulder too far WILL cause thinning of the case body. Headspace separation happens just above the case web, because this part of the case gets stretched when a case is blown forward at each firing. You're right about FL dies - when they're adjusted accurately. Whether you FL or NK size - it's a good idea to push the shoulder back a measured distance.
I developed the Digital Headspace Gauge to help shooters keep their chamber clearance to a minimum (about - .002") This gauge provides the easiest way to get this measurement.
Most dies will push the shoulder back quite a bit more than necessary, and some chambers are larger than necessary. The difference can be considerable, so it's best to measure your handloads, and get it right. Most shooters are amazed to see how far off factory ammo is compared to their particular chamber. Check this out on our website ...
Larry, your tool looks nice.
But I don't see how it would indicate actual headspace or seating distance from lands. That is, without firing a case till it's clicking on extraction, and using that as a reference/gauge zero.
Now for seating, does the indicator adapter have holes for bullets?
I'm used to using calipers with gizzies and comparator nuts myself.
If your tool makes things easier, then I'll jump in line to get one.
I love toys..
I agree that proper bumping falls under 'prevention' of case stretch. But I know of no proccess that will unstretch cases, and some cartridges will always stretch due to design(high body taper). These are known to need constant trimming.
Proper bumping could certainly reduce stretching for these cartridges.
And that would be tried and trued, rather than assumed.
Our Digital Headspace Gauge compares your handloads to one of your fireformed cases (at the shoulder). This gauge then displays the difference. (That's the exact chamber clearance that YOUR handloads will have in YOUR particular chamber.) - OR - If you have several rifles in the same caliber, and you need ammo compatability, just load for the rifle with the shortest chamber. This gauge leaves no guesswork, and there's no chance to ever get a headspace separation. Your brass lasts longer, and you'll usually get improved accuracy.
Seating depth is another issue. I've made one perfect sample round for each individual rifle (and for each different bullet type) that I load for. Then I use the Digital Headspace Gauge to set the height of my seating die - perfectly. Measuring the bullet low on the ogive exposes differences in seating depth, and helps you detect important variations in bullet shape. This also improves accuracy.
So guys how about an answer?? How thin is too thin? How do I tell when my grass has had it?
I'm sure I can read the lit on the casemaster but would appreciate your thoughts.
When your RCBS CaseMaster reads a -.003" dip in the inside wall of your case, the case is toast. Toss it out. I just wanted to show you how to avoid wasting your brass in the first place.
However, it's still a good procedure to check that inside measurement. After you use the CaseMaster a while, you'll know exactly what you're looking at, because you'll feel the pointer (and see whay it reads) as your case slips over it.
Thanks Larry! I have one of these tools but haven't used it for this yet. I'm sure I haven't been resizing in a manner that preserves my brass, but will be fixing that.