I did another load test to see if I could repeat the results from last week.
Conditions were okay, although the mirage was heavy. Distance is 200 yards. Rifle is built with Armalite AR-10 upper and lower receivers, 24-inch Krieger barrel with 1-in-8 twist and chambered for .260 Remington, SLR Rifleworks adjustable gas block, Giessele match trigger, and a Thunder Beast Arms 30P-1 suppressor. (Suppressor was attached.)
The riflesmith is John Brandstatter, Roscoe's Enterprises LLC, Pueblo West, Colorado.
The load shown in the image used Lapua cases, Lapua Scenar 139gr bullets loaded to magazine length,
42.0 grains of H4350 powder (charges individually weighed on an RCBS 10-10 scale), and Federal 210 Match primers.
So, five shots into about .852 inches gives sub-1/2 MOA. I figure that's better than good for a gas gun. Load development can now stop. This is similar to (although a little better than) the results from last week, so I don't see this as a fluke.
Temp: about 72 degrees F.
Range altitude: 5,000 feet
Chronograph: Oehler
Avg velocity: 2759 fps
Extreme spread: 21 fps
Standard deviation: 8 fps
I did test other bullets. Hornady 140-gr A-Max were inconsistent and did 1-MOA at best. Berger 140-gr Hybrid were consistently 3/4-MOA. Sierra 142-gr MK didn't even produce a good shotgun pattern, which surprised me.
Cheers,
Richard
Conditions were okay, although the mirage was heavy. Distance is 200 yards. Rifle is built with Armalite AR-10 upper and lower receivers, 24-inch Krieger barrel with 1-in-8 twist and chambered for .260 Remington, SLR Rifleworks adjustable gas block, Giessele match trigger, and a Thunder Beast Arms 30P-1 suppressor. (Suppressor was attached.)
The riflesmith is John Brandstatter, Roscoe's Enterprises LLC, Pueblo West, Colorado.
The load shown in the image used Lapua cases, Lapua Scenar 139gr bullets loaded to magazine length,
42.0 grains of H4350 powder (charges individually weighed on an RCBS 10-10 scale), and Federal 210 Match primers.
So, five shots into about .852 inches gives sub-1/2 MOA. I figure that's better than good for a gas gun. Load development can now stop. This is similar to (although a little better than) the results from last week, so I don't see this as a fluke.
Temp: about 72 degrees F.
Range altitude: 5,000 feet
Chronograph: Oehler
Avg velocity: 2759 fps
Extreme spread: 21 fps
Standard deviation: 8 fps
I did test other bullets. Hornady 140-gr A-Max were inconsistent and did 1-MOA at best. Berger 140-gr Hybrid were consistently 3/4-MOA. Sierra 142-gr MK didn't even produce a good shotgun pattern, which surprised me.
Cheers,
Richard
