I'm relatively new to reloading so I'd like to get some opinions on something I've noticed on occasion. During my load developments for my 300 win mag (Browning A-Bolt with Boss) some of the 3 shot groups have a odd pattern to them. Most groups (9 out of 10) have random spacing. But occasionally, I notice a string of three that is almost perfectly aligned horizontally but each shot moves a little more to the right (about 1/2" on each shot). When it does this it's always more to the right for each successive shot for 3 shots. I've been changing something after each 3 shot group, usually power charge amount or type or Boss setting or bullet etc. I know I need to load up more rounds than 3 of the same thing and leave the Boss alone so when I run into this I can see what the 4th, 5th ect. shot would do.
I should add that these horizontal strings happen on the first shots with a clean barrel. But other first shot groups with a clean barrel do not do this. Barrel temp does not seem to affect it. Some of the best groups of 3 I've obtained @ 100yds. are under 1/4" with a clean barrel and those groups do not string to the right nor do 90% of the other groups. I'm just about satisfied with what I've worked up so far and now have accurate low and high power 165 gr. loads and good high power 180 gr. ones.
I guess it's the clean barrel that does it, but it's strange that it only happens to specific loads.
Any ideas????
I should add that these horizontal strings happen on the first shots with a clean barrel. But other first shot groups with a clean barrel do not do this. Barrel temp does not seem to affect it. Some of the best groups of 3 I've obtained @ 100yds. are under 1/4" with a clean barrel and those groups do not string to the right nor do 90% of the other groups. I'm just about satisfied with what I've worked up so far and now have accurate low and high power 165 gr. loads and good high power 180 gr. ones.
I guess it's the clean barrel that does it, but it's strange that it only happens to specific loads.
Any ideas????