Trouble seating WLR magnum primers in Winchester .300WM brass

[wombat13]

I am having difficulty seating WLR magnum primers in .300WM brass made by Winchester (new brass). The primers will not seat flush. I'm using a Dillon 550 press given to me by my FIL. He reloaded for pistols (45 acp and .44 mag) for decades and never had a problem. I've reloaded several hundred .45 acp and never had a problem.

The Dillon manual indicated a loose shell plate causes difficulty seating primers, but I checked my shell plate and it is not loose. I tried Remington LR primers and they seat flush.

I checked the two primers with calipers and the Remingtons measure .210 and the WLR magnums measure .211. Is this .001 difference enough to cause this kind of problem?

 

[rodregier]

Just for giggle measure the primer pocket depth.

 

[LeonCarr]

A primer pocket uniformer will help your situation with the .300 Winnie.

 

[wombat13]

Just for giggle measure the primer pocket depth.

I'll do that tonight. I don't think that will be the problem though. The Remington primers seated fine yet they measured deeper than the WLR magnums. The Remingtons measured .132" and the WLRMs measured .128".