I've been working up loads for my .300 Win Mag and a few weeks ago weighed all 100 brand new Winchester W-W Super cases. I've been following the OCW method and in addition to shooting 30 rounds today (6 loads x 5), I wanted to see if a difference in case weights had a significant effect on POI with the same load. The question often arises here as to how much case weight variation is acceptable. When I weighed the cases, the lightest was 236.8 grains and the heaviest was 241.0 grains. So I loaded up 21 brand new cases (trimmed to 2.610") with 70.0gr of Reloder 22 since 70.0gr seems to be close to the OCW load for new brass based on my experience over the past few weeks. Target #1 shows the two "fouler" shots to start off the day ... case weights are 240.9 grains and 238.2 grains. The case weights for target #2 are shown on the second image along with the POI (and order shot) for each case weight/load. The case weight range for that target is 4.2 grains. I chose cases that were roughly 1 grain apart in weight for each of the five rounds.
Target #3 was shot with cases ranging from 237.4 grains to 238.1 grains ... a range of 0.7 grains. If I hadn't messed up the fourth shot, I could have had a 0.168" group!
Finally, target 2 (bottom) is a 9-shot group with cases ranging from 239.5 grains to 240.1 grains.
Target #3 was shot with cases ranging from 237.4 grains to 238.1 grains ... a range of 0.7 grains. If I hadn't messed up the fourth shot, I could have had a 0.168" group!
Finally, target 2 (bottom) is a 9-shot group with cases ranging from 239.5 grains to 240.1 grains.