I think 43 grains will be fine with a 150 grain bullet. In my rifle, 44 grs is where I stopped with IMI brass, which is just as heavy as LC. IMI brass was hot stuff in the M1a, it is good heavy brass. The best was LC, but that was not always to be had.
Ruger M77 26 " Barrel 1:10 twist
150 Sierra Matchking 39.0 grs IMR 4064 Lot 2449 LC67 CC#34 OAL 2.750"
30 April 2008 T = 71 °F
Ave Vel = 2416
Std Dev = 52
ES = 113
High = 2479
Low = 2366
N = 5
150 Sierra SP BT 44.0 grs IMR 4064 IMI brass CCI200 LC90 OAL 2.760"
30 April 2008 T = 80 °F
Ave Vel = 2749
Std Dev = 14
ES = 47
High = 2777
Low = 2730
N = 10
v.good accuracy, no increased effort on bolt lift
With an M1a, I used a max of 42.5 grs IMR 4064 with a 168 Match. Always wanted midrange loads that did not give surprises on 90 degree days!
Toasty!
Ruger M77 26 " Barrel 1:10 twist
150 Sierra Matchking 39.0 grs IMR 4064 Lot 2449 LC67 CC#34 OAL 2.750"
30 April 2008 T = 71 °F
Ave Vel = 2416
Std Dev = 52
ES = 113
High = 2479
Low = 2366
N = 5
150 Sierra SP BT 44.0 grs IMR 4064 IMI brass CCI200 LC90 OAL 2.760"
30 April 2008 T = 80 °F
Ave Vel = 2749
Std Dev = 14
ES = 47
High = 2777
Low = 2730
N = 10
v.good accuracy, no increased effort on bolt lift
With an M1a, I used a max of 42.5 grs IMR 4064 with a 168 Match. Always wanted midrange loads that did not give surprises on 90 degree days!
Toasty!