Sierra 120 Tipped Gameking

[grayfox]

Grayfox-Your points of impact on the 30.3/30.6/30.9 were all awfully close, suggesting a node. Have you thought about playing with seating depth to see where you optimum accuracy lies. I have four sets of six rounds using CFE, Lever, PPV and AR Comp set at 2.280 OAL to start my testing. Look forward to more of the collective test results.

Looks like that, but there's 2 reasons why I don't typically trust that:
1. These shots were with a magnetospeed, which does alter the point of impact, although in theory it should do all shots the same way -- sometimes it doesn't.
2. I don't trust my own steadiness enough to rely strictly upon impact points on paper, and these were only 3 shots each anyway. I'm not as rock-solid as some guys on here.

My method uses a different approach, based on Chris Long's OBT theories (appeals to the eng-geek in me).
1. I shoot a few over a spread of charges to establish a chrono-MV ladder vs charge, graphically. If the result is relatively linear then it tells me the powder/combo could be a useable one. (sometimes I have gotten pretty zig-zaggy graphical results from a powder on this step, so I usually move to another powder). I define a "well-behaved" powder as one that shows "pretty much linear" increases in MV for linear increases of powder charge, over a reasonable charge-volume case combo. That's what powder should do anyway!
2. I will shoot a narrower charge spread, with 4-5 per charge, looking for a node close to a mechanical one predicted by Long's theory (longitudinal pressure wave-travel). For a 22" barrel and 120 class bullet in Grendel, this usually means 1 is close to 2520 fps give or take.
3. I pick one from this narrower spread, close to the node, which usually has the lowest or close-to-lowest MV spread in SD. Then shoot these while changing OAL length to find the best group.
4. Then I can zero that group-charge for 100 yds.