ORIGINAL: skeeter 7MM
I had a 4 time loaded rem brass seperate just above the belt in my 7mm rem mag the other day while busting a yote. Bullet hit the intended target but exctration of the case was difficult, it ended up seperating leaving the remaining portion in the chamber but when I removed the bolt and tipped it up the case fell out. At the shoulder it has crimple marks and powder burn where I assume the seperation took place. A scope shows no effects to chamber or bore according to my gunsmith. Test fires at the range proved everything is normal and where it should be. Load has shot fine for a couple of years, no pressure signs and this is the first time such a thing has happened to me.(have seen it on the range before just not personally). Powder is RL22 same lot number as previous.
Got me thinking about brass and sizing technique. I was taught and still FL size my brass. I inspect the brass prior to reloading and always work up with different components even though a load may be proven previously. I rarily tumble anymore, just wipe them down and reload. Think I am being particular about my reloading techniques but when something like this happens you wonder just a tad??
It will continue to happen, regardless of the make of the brass you are using, BECAUSE:
Your rifle has a "generous" chamber, and your cases are stretching a little in head-to-shoulder dimension on firing each time. You then push the shoulder back on resizing, and every time you fire it, it stretches again until the brass becomes fatigued and cracks-then it leaves the front part of the case in the chamber while the head is extracted! Belted (and rimmed) cases have this problem a lot.
The solution is to set your resizing die out a little, so the shoulders of your cases stay put when you size the brass.
You can't really prevent the new cases from being stretched once, unless you go through the drill outlined below with new brass. But you CAN prevent it from happening again and again. If you feel a need to "full-length size" each time, "smoke" a lubed case with a match or candle, screw the sizing die out one thread, then screw it back slowly, testing it each time you turn it in slightly, until the shoulder inside the die just barely touches the case shoulder, then lock the collar at that point.
Personally, for brass fired already in my rifle, I only size enough of the case to get a firm grip on the new bullet......
IF you wish to totally eliminate this problem, starting with new cases, youexpand the case mouth up to .30, or even .338, caliber, then neck it back down to 7mm in increments very gradually, creating a "false shoulder" on each case that you adjust for headspace by checking it in your rifle's chamber as you continue to size it back down, stopping the sizing process when you reach the point that you can JUST BARELY close the bolt on the case with some force. You size all your new brass this way, and you end up with a bunch of funny-looking cases, but ones that are prevented from stretching on firing the first shot by the false shoulder you created to compensate for the slop in your chamber dimensions. I know this is a PITA, but it is the same process you have to go through when creating wildcat cartridges, and it will absolutely prevent case loss due to stretch.