I've watched a couple of youtube videos by Erik Cortina and decided to try one of his suggestions, which is to seat bullets deeper in .003" increments. My normal procedure has always been to use much wider increments, like .020" or even .025". My old .243 AI is still a great shooter even with close to 3,500 rounds down the tube and I haven't adjusted the seating depth on its loads for a while, so figured it was a good candidate for testing.

Used a Stoney Point OAL gage to find the jam length, it was a good .1" longer then when last checked, then I loaded six sets of four rounds each starting at .020" off and increasing in .003" increments.

This morning was very calm with winds at 2 mph or less so it was a good time to try these. The picture below shows how the groups progressively tightened up as the bullet seating depth increased. The colored bars are 1/2" wide, aiming squares are 1.5", rifle is a Model 700 with a Pac-Nor Sporter contour barrel, Sierra 85 HPBT, scope is a good ol' Leupold VX-II 3-9x40. Cases are 10x fired but freshly annealed, neck sized and shoulders bumped .002".

It looks like this ended up right on the verge of an accuracy node so I'll load up some more starting at the final seating depth and continuing the seating progression to see when groups start opening up again.

Fwiw, I have a few issues with Erik's videos and also the statistical significance of one group at each depth but he does get results which can't be denied. This series of groups definitely shows a trend and warrants further exploration. If this works well I might rework up some loads for a couple of newer rifles which don't seem to be performing up to their potential.


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