Follow Up range report

Previously, I had mentioned a test I planned to conduct regarding a heavy weight (match grade) ammo in my AR15 with a 1:9 twist barrel.

"Conventional" wisdom states that a heavy bullet (over 70 grains in weight) will not be sufficiently stabilized in a 1:9 twist barrel. Most shooters go to a 1:8 or 1:7 twist barrel to stabilize the 70 grain+ bullets.An under-stabilized heavy bullet will keyhole (strike the target sideways) - often by 100 yards.

A while back, I did some research on the topic, and found that in every instance of confirmed keyhole activity, the gun was an M4 type barrel (14.5 inches long with a 1.5 inch flash hider to make it "legal") in conjunction with 70+ grain ammo.

Also, I discovered that people with bolt-action .223's often shot 70+ grain ammo - and their rifles often only had a 1:10 twist. Also, their barrels were frequently 22-24 inches in length. They also got superb accuracy from the setups with the heavy bullets.

So would the 20 inch barrel with a 1:9 twist stabilize a 75-grain bullet? I used Privi-Partizan (a.k.a. "PPU") match grade 75-grain bullets. I discovered several things:

• 75-grain "PPU" ammo definitely does stabilize in my rifle. No keyholes at 100 yards.
• 75-gr ammo shoots sub MOA in my rifle. 10 shots all inside the 1 inch circle. 
• Point of impact was almost identical to the 62-gr ammo I had sighted in with. 
• I think this rifle and ammo combo would serve well in competition.
• Sighting in ACOGs is an easy task.
• If ACOG's were allowed in competition, I'd use one.