I went to the range today looking to put the seating depth mystery up to its first test. I was using my 175Gr SMK load and placed the bullet 0.005″ closer to the lands for each five shot group which looked something like this:
The final test would have the bullet jammed into the lands 0.005″, thus I had to be cautious and watch closely for signs of high pressure as I shot each group. The bolt became stiff to lift on the last two groups, but no other signs of high pressure were noted.
Starting from the top left, group 1 and 6 were my control groups using the original 2.075″ measurement. Groups 2 thru 5 were the test subjects. I am very pleased to see that the groups tightened up as I moved the bullets forward.
Groups measured at:
- 0.752″ I pulled that one flyer so it should have been closer to 0.368″
Group 3 and 4 are the best by far. I now know that these bullets are going to like sitting very close to the lands. Somewhere between 0 and 5 thou jump will be the optimal position. I plan to confirm this with another test shoot.