I had a partial case head separation using a 1.8oz buffer

[pmc847]

I’m into my load development for my AR15 6mm ARC Bartlien 26” 7.25 twist by Paul Craddock.

I’m resizing 6.5 Grendel using L E Wilson bushing FL die. I also anneal my brass.

Here is what I’ve observed.

SAAMI specs cartridge .4410 @ .200 from base and .4315 @ 1.00 from base
specs chamber .4426 @ .200 from base and .4325 @ 1.00 from base.

Hornady 108 match ammo
cartridge .4350 @ .200 from base and .4275 @ 1.00 from base.

Fired brass
cartridge .4425 @ .200 from base and .4320 @ 1.00 from base.

Resized with L E Wilson die
cartridge .4350 @ .200 from base and .4250 @ 1.00 from base

Measurements taken with Mitutoyo CD-6" ASX to the best of my ability.

Question is, is this die re-sizing the body too much? I am getting the shoulder bump I need and use Short Action headspace comparator with datum B .350 insert.

Shouldn't, ideally, resizing be the same as SAAMI cartridge spec. It seems that the difference from fired brass and resized brass of .0075 is a lot. I know ammo manufactures need to have adequate clearance for all platforms but I’m looking to load for my specific rifle. My concern is over-working the body during sizing. This leaves a noticeable ring about .200" from base. I just checked my 223 to compare. It resizes the body by about .002 to 0025" with no noticeable ring.

John Whidden suggest about .002-.0025 with about .0001 spring back. I ordered a custom die from Whidden, 8 weeks to go.


Cheers
Philip