I am currently trying new hand loads that can reach out to 1,000 yards accurately from a cold bore, one to two shots from my 300RUM. I am currently running the 180gr. Nosler Accubond with the IMR 4350 powder. I am using 80.3 grains of powder and the overall length of the round is 3.550". This past weekend I shot a 5 round group. Three rounds landed .115" apart but the last two made the group grow to just under .5", (operator error). This load is great when the barrel is very hot. When the barrel is at room temp, the group is about an inch. At about 3125 feet per second, it is fast but I want it faster and with a tight cold bore 3 round group. I tried RL25 with 95.3 grains of powder and the group with right at .375 inches with one flyer. The next day I shot the same three round group and it grew to about a 2" group. The weather was warmer on the second day and I read that the RL25 is temperature sensitive. I was going to try the IMR 7828 and or the H1000 next. Does anyone have any information on what I could use or do to get that group tighter? I seat the bullet at the max casing dimension, test for pressure, once pressure is achieved I play with the bullet depth. Any help would be greatly appreciated.
Thanks.
Thanks.