Excessive case stretch????????why?

[Craigyboy]

Just a quick question, why is it I am having to bump the shoulder back on every firing for my tac20? I am not loading very hot and am using lapua brass but I find after just one firing they are tight to chamber, they can be chambered ok but just tight, bumping them back every firing is no big deal its a quick process and I have the bump die set just about perfect, just curious as I have never had to do it so much before.

 

[Tommie]

Did you have this problem with other brands of brass?

 

[Craigyboy]

I havent tried any others tommie.

 

[Tommie]

I'd try switching brands of brass first.

 

[Travelor]

What action are you using and who barreled it?

 

[Craigyboy]

I am using a cooper model 21 barreled by a good smith over here i the uk, he headspaced it pretty much spot on but they still seam to grow out somehow.

 

[yat3b35]

could be your case length is off causing tight chambering. Make sure you trim to proper length.

 

[Rustystud]

Traveler hit it on the head....

The best Smith screw-up from time to time. I am no exception.

Check the headspacing with steel gauges they don't lie. Then set your dies using the go gauge, then set it down another .002 for brass spring back. If your gauges are in SAAMI spec your case should stablize after the first fireforming.

Fireform and trim. You should be able to get 10-15 firings before having to anneal an/or trimming again.

I'll bet you $5.00 that it is opperator error on the part of the loader. Is your die bottoming out on the shell holder and need to be trimmed off? Or does your die need to be backed out and not bump the shoulder so much?

Rustystud