Forster shoulder bump dies

[memilanuk]

Hello,

I'm experiencing a little weirdness with a shoulder bump die from Forster... wondered if anyone out there has some experience w/ them and would care to take a stab at it.

Basically... I can't control the headspace with the darn thing. I've used Redding body dies and Type 'S' F/L dies for years, but figured I'd try one of the new shoulder bump dies for a change. I can't get it to bump the shoulder *less* than 3 thou. I've tried in both a Redding Big Boss press, and in a Forster Co-Ax. I've literally unscrewed the die a full turn and more,at what, 0.071+ thou per revolution) to where the die barely touched the neck and I had to keep screwing in the decapper pin to get it to punch out the primer - still bumped the shoulder 0.003".

I'm measuring with a Hornady/SP comparator set, using the recommended 0.420,'E') headspace insert on a set of Mitutuoyo Digimatic 6" calipers. Fired cases measure 1.811",relative measurement); sized cases measure 1.808".

Hopefully I'm just missing something simple, but I'll be dipped if I can figure it out. Any help would be greatly appreciated.

Thanks,

Monte

 

[tripcrow]

Monte, from what I gathered the Forster bump die doesn’t get the neck shoulder junction so good. See Forster drawing of how it sizes. Your headspace gauge may be taking its reading right at the junction. Try a larger tool that’ll read off on the shoulder more and see what you get.

I always wondered what was the sense in bumping back the shoulder when the sized case is just going to then headspace on the unsized NS junction anyway??

Bill

 

[memilanuk]

Found the problem... cratered primers,from big firing pin hole, not hot loads) giving false readings.

Thanks,

Monte