Understand the optimum Overall Case Length ?

[searlest]

I am in the process of putting together a 7MM SAUM

PROOF Research Carbon Prefit Barrel 24" Length, 1-8.4 Twist, Sendero Contour,

Tikka T3, Action

Barrel is throated to allow seating heavy for caliber bullets closer to magazine length - Max COAL w/ 180 Hornady ELDM at 3.208".



OK now for my question I am ordering a Custom Lee quicktrim die, in order to do this I must submit the below data I would like to understand the optium dimension for “D” with the set up above? How does altering the over all case length effect accurancy and performance?

Both attachments are from Lee's website

 

[pods8 (Rugged Stitching)]

When folks talk about Cartridge Over All Length (COAL) it has nothing to do with the trim length of the brass and only related to where the bullet is seated. You don't need to change the D unless you have some wildcat chamber.

 

[Wapiti1]

D should equal the "trim to" length in the reloading manual or SAAMI cartridge print. A standard trim die is fine for all uses with a SAAMI cartridge.

Jeremy

 

[wind gypsy]

Agree with the two comments above.

Also, did you have a proof blank chambered by a gunsmith or are you having the throat of a proof prefit lengthened? Id assume that proofs prefits use a SAAMI spec chamber?