I was trying different seating depths for my .308 Win, using a Lee seating die. I had 20 resized cases with the same amount of powder in each. I used 150gn Speer boattails, and seated 10 of them to 2.85 overall length. Then I adjusted the seating stem only, to get an oal of 1.75 inches. After seating the remaining 10 that way, I noticed that the cases were bulged into a large donut ring where the body start to taper to the neck. This bulge was the same on all 10 cases, and was large enough to prevent chambering. I took a resized case and slid it into the die and adjust the seater all the way from one end to the other without interference, so I don't think it was hitting the case. I didn't adjust the die body between the first 10 (which were normal) and the secong 10 loads. Any ideas on what caused this? I'm stumped!

Screw your seating die out a couple of turns. What's happening is that the die is trying to crimp the case necks into the bullet, and the brass has no place to go, so it shortens the case by bulging the shoulder junction! Just move the die out enough that it stops trying to crimp!!

Made the same mistake myself several times. It comes from turning the die in too far. Back it out a few turns.

I am just wondering, you have not mentioned that you first trimmed all cases to the same length, I have seen far too many people that run brass through their sizing die and then try to crimp, and they find out that each case has verying lengths after sizing and they just happen to have the die set to minimum and the case is too long, so then the crimp is pushed too hard.

iv'e done it too. my buddy missed a 60 lb coyote because of it. i sold him my 284 and had quickly made a batch of 100 grn food for it. unfortunately my die was set for 140's. had 13 of the 20 cases "donut" as you mentioned. i never even noticed. haven't done it since.
woofer

eldeguello has correctly diagnosed this problem and given you the cure. Do it.

Sorry, I meant 2.75" oal.
Thanks for the advice everyone!

[ 12-20-2002, 05:42: Message edited by: savageshooter ]

Maybe I'm missing something here, but I thought he said that he moved the seating stem only, not the die body. And just what would the chance be that his first ten cases were shorter than his second ten.

It doesn't matter. If the seating die is properly adjusted (meaning the shell holder does NOT touch the bottom of the die and has at least 1/8" gap between the two) then the die will not try to crimp the case mouth into the bullet, meaning the shoulder won't bulge and the cartridge will chamber.