Trick to jumping bullets???

[bowhunter42]

I usually measure my chamber length and then my mag length to see what kinda jump im looking at. I then load to 5 thousadth's off the mag length and load 6 rounds, then load 6 more 40 thou off that and 6 more 40 thou off that down to around saami coal. I usually get about 4 groups of six rounds. one of these groups always shoot alot better than the others. I then use that as my starting length to develop a load for that rifle. I have found that something as simple as changing a primer can effect the grouping of a load. In my 300 win I found a load that shoot really well but my ES was up in the 50's I changed the primer from cci to federal and my Es dropped into single didgits but my groups opened way up. I changed to win primers with the same result. back to CCI primers and I increased the powder charge by .5 grains and both my group size and ES tighten back up. ES down to 11fps and Groups down to 1/2 inch. I am shooting Berger's out of it and long range performance is outstanding.

[tim jurczak]

Here is the latest. I went to the range with some 129 gr interbonds loaded at mag length. I did not even bother to measure jump this time as it has to be at least 50'thou. First I started working up with WC872 and as usual 1 1/2 groups. I brought my chrono along this time and realized I was getting ES around 75fps. Upper loads hovered around 3500 fps. Then I cleaned the bore and tried IMR 7828. First two groups measured 3/8" and 1/2"! Hurrah! Moved up anouther grain pressures were too high and velocity had peaked. Also groups got larger. ES with 7828 were around 40, and top velo was 3455 fps. I guess the moral of the story is what?
I have been pondering every responds I have received and plan to try some barnes bullets. I have already switched primers and am going to see how it shoots single shot. Thanks, tim