Thread: Testing a conventional approach to load development

Originally Posted by gimp

So conclusion - with this rifle, bullet, brass, powder and shooter combination it is not possible to identify any difference in precision between loads with different seating depths by testing with 3 shot groups, at .003 inch increments of seating depth (as recommended by Erik Cortina, if he isn't the person to listen to for this then who is ?). Or 20rd groups of same.

First off I’d like to say this is super interesting and “ good on ya “ for going to the effort to both conduct these tests and to document them so thoroughly

I’m doing some load development at the moment for my 6.5CM with Sierra 130gr TMK projectiles.

So my initial test is always for Powder charge weight ( using 2209 powder ) with the projectile approximately 45 thou off the lands . I use the word approximately because I have yet to use / find a method that is spot on accurate when measuring throat length .
Starting at 1.0 gr below Sierra’s listed max charge I loaded up 6 rounds of each powder charge going up in 0.5gr increments ending up 0.5gr over their recommended max .
I shot those rounds and experienced zero pressure signs , all shot acceptable groups ( below 25mm at 100 yrds ) with an apparent improvement as the charge weight increased . All of this means “ Diddly Squat “ in the grand scheme of things but I wanted to find my upper limit of safe powder charge .
Now I have just loaded up another batch of loads using my chosen powder charge but with a selection of different seating depths. I make 10 thou increases in CBTO length.
So now in theory I am going to test 45 thou / 35 thou / 25 thou / 15 thou jump to see if things tighten or loosen as the seating depth changes.
I can’t understand why anyone would F*#k around with 3 thou changes , maybe in the world of Benchrest / F Class , but not in the world of Hunting / Factory barrels.
This seating depth test is just to see if there is an obvious trend developing either good or bad and then and only then will I load a decent amount of the chosen brew and shoot multiple 10 shot groups .