300 win mag sierra 220 loads


Well-Known Member
Jul 17, 2001
Walla Walla, WA
It was quite foggy this morning. I could not see the target at 100 yards so I moved closer to 65 yards. Is it reasonable to expect that if group size was 0.3" at 65 yards then it would be 0.45" at 100 yards? I was shooting the Sierra 220 Matchking in a long throated 300 Win Mag. This bullet is touching lands at an overall cartridge length of 3.565". I started load development with the bullet just touching lands. I am using Federal cases and Federal 215 Match primers. The rifle is a hunting rifle (8.3# without scope and sporter style stock) so I am not expecting 0.25" groups at 100 yards. I decided to test RL25 initially. Perhaps I will also try H1000. Groups were 3 shots and again they were at 65 yards due to fog. I started with 71 grains and got a 0.77" group. 72 grains gave 0.54" and 73 grains gave 0.31". I think I can go up more in powder. Also I have not messed yet with seating depth. Are any of you using this combo of powder, bullet and case? If so where have you reached max charge and where do the bullets generally like to be seated in relation to the lands? What kind of velocity should I be able to get from a 26" barrel? Would H1000 be better? Thanks, Rufous.
I went out again this afternoon. It was not nearly as foggy. I set the target up at 200 yards at tried the 73 grains of RL25 load again that gave me a 0.31" group at 65 yards. It was 1.78". Then I tried 74.0 grains and got 1.25". 74.5 gave 0.5" and 75.0 gave 0.74". Looks like 74.5 grains is my load. I hope to try it tomorrow at longer ranges. I have not yet started fiddling with seating depth. I just have it touching the lands, but if I can duplicate that 1/2" group at 200 yards I probably will just go with that. I do not know what the velocity is but am guessing it is in the 2750 to 2800 fps range. Rufous.
I have very good results with H-1000 in the .300 but I mostly shoot 190 Sierras and Speer match. I have also had good accuracy with RL-22, but case-life was shorter with the loads that shot well.

I do not believe that your results at 65 yards can be interpolated for 100 yards, just doesn't work that way. No doubt you are on the way to some great shooting loads but 100 yard tests are 100 yard tests. Just like we do not get 10 inch groups at 1000 yards from a rifle that shoots 1 moa at 100 - lots of variables involved.

My .300's like the bullet to be seated as close to the lands as I can, I back off a couple of hundredths. Magazine length can become a factor if you have a long throated chamber.
Good luck with your load development.
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