I was working up loads yesteraday and was putting them across the magneto-speed chronograph yesterday and observed something kind of puzzling.
The powder is imr 4007 ssc
two different cartridges, 22-250 and 243
in the 22-250 with 55 grain sierra #1360 bullet, max load in Hodgdon manual is 39 grains, and should produce about 3786 fps, I get 3577 ave, sd of 1 across 3 shots. so about 200 fps slow.
in the 243 with an 80 grain sierra blitz bullet, max load in the Hadgdon manual is 45 grains and should produce about 3319 fps, and I get ave of 3409 fps ave, sd of 6 across 3 shots, so about 100 fps faster....
I like the low spread/ speed range I was getting across the shots, and the groups were quite nice
both set ups were new rifle barrels, new brass, and federal 210 gm match primers
I am curious as to why this may be. one rolling quite a bit slower and the other a fair amount faster...
The powder is imr 4007 ssc
two different cartridges, 22-250 and 243
in the 22-250 with 55 grain sierra #1360 bullet, max load in Hodgdon manual is 39 grains, and should produce about 3786 fps, I get 3577 ave, sd of 1 across 3 shots. so about 200 fps slow.
in the 243 with an 80 grain sierra blitz bullet, max load in the Hadgdon manual is 45 grains and should produce about 3319 fps, and I get ave of 3409 fps ave, sd of 6 across 3 shots, so about 100 fps faster....
I like the low spread/ speed range I was getting across the shots, and the groups were quite nice
both set ups were new rifle barrels, new brass, and federal 210 gm match primers
I am curious as to why this may be. one rolling quite a bit slower and the other a fair amount faster...