I decided to give the OCW test a try with my .30-06, and I was hoping some of you might help interpret the results. If you're not a fan of this approach, I'd also be interested in hearing your thoughts. The idea, of course, is that group POIs that print similarly across consecutive powder charges correspond to a period of "rest" in the barrel's vibrations. This makes a charge in that range highly insensitive to pressure variations caused by temperature, brass inconsistencies, primers, etc.
H4350 was the powder, and the 165 Sierra Gameking was the bullet. If you look at the first picture, I loaded from 56.9 to 59.0 in 0.3 grain increments. Hodgdon lists 59.0 as their book max with this bullet (49,400 CUP), while Sierra (inexplicably) lists max as 54.1. I can't find another load book that even comes close to that absurdly low number, so I went with the powder manufacturer's max charge. I had no pressure signs whatsoever.
Looking at the results, it appears to me that there's a range from 57.2 - 57.8 where things are very consistent, and I saw very, very little deviation in velocities across the chrono with these three charges. The POI of the three groups is within 1/8 - 1/4" of one another, which would equate to clustering in a standard ladder test.
I'm inclined to call 57.5 the OCW and experiment with seating depth. Here's a zoomed photo of the three groups in question:
Thoughts, criticisms, or does anyone interpret the groups any differently? This is my first OCW test.
OCW Test (30-06, H4350, 165 Sierra Gameking)
