Thought I'd start a 300 Remington Ultra Mag thread. I've been playing arround with one for a few month's now. Here's a load I'm working on for a One Mile Shoot we're going to have come spring.
My goal was to get the Seirra 240 SMK bullet up and over 2950 so that it would be super sonic at 1800 yards. What I found is that you run out of case with H50BMG powder and I got pressure signs before I got there with H1000. So back to Retumbo I go. I didn't have any when I started and was just wasting time without it. So far I've reached 3044 with out any sign of pressure yet. This is on 70 to 80 degree days so hot weather could be another thing. My last latter test was 90.5 to 92.5. Case capacity looks to be about to the bevel in the shoulder. There's 2 or 3 grains still before a compression load. I'm getting good groups so far and think there is still room for more speed. Here's the run down for the number junkies.
Group #1 five shots @ 90.0 Retumbo, 240 SMK, WLRM primer and RP brass fired four time so far. Shot for base line to compair to latter test. Group was .7 on a clean bore. True measurements at 12'. I didn't add back any for muzzle vel.
2982
2989
2979
2982
2986
2983 Avg.
Latter test after first group. Made a mistake and not checking barrel temp. Should have anticipated lower velocity from expansion. Anyway I believe on a cold barrel like the first group vel. would be higher. Shots are in .5 grain intervals from 90.5 to 92.5
2976
2982
3003
3016
3044
Muzzle vel. should be 9 to 12 FPS faster so I'm happy with the out come to say the least. I'm well above my needed vel. to reach 1800 yards and was able to shot two sub inch five shot groups later at 200 later in the day. I'm using a GAP built stick by Moon. It's a Stiller Predator with a Bartlein 1/10 tube. This thing will shoot 1.25 groups at 400 on windy as hell days using 210 Bergers. They'll be killer at 1000 just not the pill I want for a mile. Cheers,Donald
My goal was to get the Seirra 240 SMK bullet up and over 2950 so that it would be super sonic at 1800 yards. What I found is that you run out of case with H50BMG powder and I got pressure signs before I got there with H1000. So back to Retumbo I go. I didn't have any when I started and was just wasting time without it. So far I've reached 3044 with out any sign of pressure yet. This is on 70 to 80 degree days so hot weather could be another thing. My last latter test was 90.5 to 92.5. Case capacity looks to be about to the bevel in the shoulder. There's 2 or 3 grains still before a compression load. I'm getting good groups so far and think there is still room for more speed. Here's the run down for the number junkies.
Group #1 five shots @ 90.0 Retumbo, 240 SMK, WLRM primer and RP brass fired four time so far. Shot for base line to compair to latter test. Group was .7 on a clean bore. True measurements at 12'. I didn't add back any for muzzle vel.
2982
2989
2979
2982
2986
2983 Avg.
Latter test after first group. Made a mistake and not checking barrel temp. Should have anticipated lower velocity from expansion. Anyway I believe on a cold barrel like the first group vel. would be higher. Shots are in .5 grain intervals from 90.5 to 92.5
2976
2982
3003
3016
3044
Muzzle vel. should be 9 to 12 FPS faster so I'm happy with the out come to say the least. I'm well above my needed vel. to reach 1800 yards and was able to shot two sub inch five shot groups later at 200 later in the day. I'm using a GAP built stick by Moon. It's a Stiller Predator with a Bartlein 1/10 tube. This thing will shoot 1.25 groups at 400 on windy as hell days using 210 Bergers. They'll be killer at 1000 just not the pill I want for a mile. Cheers,Donald
