Here are the facts as they stand:

I have a .300 Winchester Magnum that I want to test with 180 grain Accubonds. I have the following powders and quantities available (with the guns I use them for also listed).

My question is which powder would you start with (may not end up with) considering a desired mix of high velocity and accuracy (sub m.o.a., and yes the gun is capable)and taking into consideration such things as temperature stability (I hunt in 85F down to below 0)

Here is what I have:

8 lbs of IMR 4831 - No current use (working on a .270 Winchester load)

5.5 lbs of H1000 - Current use is in a 200 grain Accubond load for the gun in question.

4.5 lbs of RL22 - Current use in in a .257 Weatherby with 100 gr. TSX.

1.5 lbs of IMR 7828 - No current use

1 lb of RL25 - No current use

Question:
What powder would you start with?

Choices:
IMR 4831
H1000
RL 22
RL 25
IMR 7828

 

I didn't vote. IMR4831 may not give the absolute highest velocities, but it should give fine accuracy and is quite fine in different temperatures. Besides, you've got lots of it!

81.0 grains H1000!!!!!!!!!!

I have found that 75.5 gr RL-22 will produce near 3100 fps while delivering sub moa groups

Work up to 77 or dare I even mention 78 grains of IMR 7828 and velocities and accuracy, as well as low SD's and ES will be yours. Not all rifles will want to handle 78 grains, butif velocity comes with less powder, so be it.

In my 300WM, H4831sc gives me the best accuracy and is temperature stable. RL22 gives faster velocities but is not temperature stable in my experience. H1000 would be your best choice given the powders available to pick from.

The best groups I have ever shot in my 300 win were 80 gr H 1000 and 180 Accubonds. At 81 gr the groups open a bit but it might have been me. Further testing tomorrow.

I agree with molar 1. I use 75.5gr of RL-22 with Nosler Partitions. It is Elk disaster. Great power and groups.

I voted IMR 7828, but some rifles have done better with RL22. 308 Sako is right on with 78 grains of 7828 and 180s. Funny thing tho, the Ruger loves RL22, and the Sendero does even better with 7828.