Using the same AR-15 now updated with Timney Trigger, Leupold scope and mounting system I shot in single shot mode with 77 grain Nosler Custom Competition bullets and 23 grains of Reloader 15. The cartridge overall length was 2.435 inches. I expected the rifle to shoot tighter groups at least 1 inch at 100 yards as the bullet was closer to the rifle lands. Best case was one group at just over 5/8 inch and two groups at around 1 1/4 inches. This is good but this rifle can do better, I think.
Back at the reloading bench today, I tried three different powders but I really did not want to shoot them in single shot mode so I shot them at just under the max cartridge overall length of 2.260 so they would fit in the clip. I shot 3 shot groups at 100 yards with wind under 5mph.
GROUP# BULLET POWDER SPREAD
Group 1 69 grain Nosler CC Bullet with 23 grains Varget 1 3/4 inches
Group 2 69 grain Nosler CC Bullet with 23 grains Varget 1 3/16 inches
Group 3 69 grain Nosler CC Bullet with 23 grains Varget 1.0 inches
Group 4 69 grain Nosler CC Bullet with 22.5 grains IMR 4895 1.0 inches
Group 5 69 grain Nosler CC Bullet with 22.5 grains IMR 4895 1 1/4 inches
Group 6 77 grain Nosler CC Bullet with 23 grains RL-15 1 1/16 inches
Group 7 77 grain Nosler CC Bullet with 23 grains RL-15 1.0 inches
Group 8 77 grain Nosler CC Bullet with 23 grains RL-15 1.5 inches (two of the bullets are 1/2 inch apart, one looks like a flyer)
Each group had at least 1 group at 1.0 but the 77 grain Nosler CC has two groups (6 &7) basically at 1.0 or 1 MOA and the other 77 grain group may have a flyer. This preliminary data was expected that the heavier bullet will outperform. From a Mil-Spec Semi-Auto Carbine with a 16 inch barrel this is very good. Thus it translates to keeping 6 inch groups at 600 yards and 10 inch groups at 1000 yards if there were no wind. I need to repeat this test with 77 grain bullets but at 150 yards, the farthest at my club before trying 600 yards.
Group 1 was way out of line and it is likely that I was not warmed up and relaxed. Hitting the bench cold can sometimes do that. Thus I think that the Varget Group 1,2,3 needs repeating after a warm up of a few practice shots. I used the scopes power at 12x to split an orange 1 inch square on each target into 1/4 inch quadrants as I squeezed the trigger.