Author: britrifles
Subject: Tweaking my Varget Match Load
Posted: October 26 2024 at 4:56pm
I think a match grade primer would reduce the standard deviations a bit more. Match grade primers have tightened up SD’s in my .308/7.62 loads and it did show up at 800 and 1000 yards in my DCRA No. 4 as reduced vertical spread on the target. One of these days, I’ll try the CCI BR-2 primer in my No. 4(T) load to see if it further reduces group size.
Subject: Tweaking my Varget Match Load
Posted: October 26 2024 at 4:56pm
I think a match grade primer would reduce the standard deviations a bit more. Match grade primers have tightened up SD’s in my .308/7.62 loads and it did show up at 800 and 1000 yards in my DCRA No. 4 as reduced vertical spread on the target. One of these days, I’ll try the CCI BR-2 primer in my No. 4(T) load to see if it further reduces group size.
As odd as it might sound, I don’t see a correlation of muzzle velocity with vertical position of bullet impact on the target (within the same charge weight) with this load in the T. Obviously, larger deviations in powder charge do make a difference, but it needs to be more than +/- 0.1 grains to show up on the target.
Based on the OCW tests, the vertical change in group MPI at 600 yards was 3.6 MOA over a 2.4 grain charge weight range. That averages out to 1.5 MOA/grain. For charge weights thrown within +/- 0.1 grains, that’s just +/- 0.15 MOA (less than one inch at 600 yds). That’s hardly noticeable for these rifles. However, there are OCW nodes where adjacent charge weights show group MPI clustered together. That’s the whole point of doing the OCW test.
I found that 40.0, 40.3, 40.6 and 40.9 grains loads all shot into a group of just 1.8 MOA vertical extreme spread of all 12 shots (three shots for each load). Pretty remarkable. Goes to show that weighing charges does not do what we think it does….