How close to the belt should your dies resize a belted mag case??

Here's the scenerio. I load ammo for a friend with 3 custom wby 270's made by a very reputable rifle maker. All are tack drivers. He DOESN'T do a good job of keeping spent brass segregated between the rifles. (YEP WE ALL KNOW THAT'S THE START OF THE EVIL). Anyhow after resizing I have trouble with some of the shells chambering in all the guns. I've come to find out that when measuring just ahead of the belt on a new case it measures .506. AFter a mild firing most of the brass measures .511. According to speer the dimension should be .512. BUT I find shells that have grown to .514--these must be coming from one of the guns. (Apparently he has a loose chamber in one of the guns.) Should I expect my dies to get all the way down to the belt and get that area resized?? From looking at most my mag brass the sizing stops somewhat shy of the belt.

INPUT PLEASE.??

I always thought this was a headspace problem but fiddling today I found what it is--now I'm just wondering if there is a fix other than letting him buy expensive new brass OR making darn sure he keeps it segregated.

The fix is to keep the brass segregated.This is a common problem when cases from more than one gun are mixed whether they are belted or not.

Sounds like one of those guns might have an eccentric chamber, which isn't all that uncommon. That was the reason that guy from Florida started marketing that collet die that size down near the belt.

Your dies won't size all the way to the belt. You'll see the "pressure ring" right after you size and before you wipe the lube. That's as far as they size. I load for a bunch of folks but that's one I don't think I'd continue.

Sounds like a test case for Ni brass, but that would only fix 2/3 of the problem! As for .270 Wby. brass, the problem will only get worse as it is my understanding that Remington dropped their 7 m/m Wby brass. Sounds like a collet die at the least, or a custom one is in your future.

I'm not much of a believer in sizing cases to minimal specs, as this usually causes more trouble than its worth. That's something nobody wants. I'd look for a Wilson case length gauge and go from there.

Simply look inside the base of your full length sizing die. You should see a relieved area at its mouth. That's for the case belt.



It will size all the way to the belt to industry-accepted tolerances for all factory chambers. If only the .514" heads are the problem, sizing to the belt should solve the problem even in these custom chambers.