We picked some good loads for our new SHILEN 20" Barrel AR15, and then went to town testing groups.
I eliminated generally 1 shot from each group, last shot, first shot sometimes a flyer. So I noted that. The first group was upper left, it it took 2 shots for group to settle in, then they were all dumping on small spot. Typically, all these groups had an 8 shot string that dumped on 1 little spot. I would probably settle with any of these primers and be happy...but the CCI won objectively here. barely. SD was 10-18 typically.
Please keep in mind...both of these bullets are NOT MATCH TARGET bullets, these are typically hunting/defense bullets.
25.0 Grains Benchmark
62 Grain Speer Gold Dot 2.250
23.7 grains Benchmark
64 Grain Sierra Game Changer 2.250
PISTOL PRIMERS (2nd from top)
Fiochhi ZETA PI lead free small pistol primer.
While you can use pistol primers in rifles, and it will fire...you typically CANNOT use rifle primers in pistols because pistols do NOT strike the harder, thicker wall/face of the rifle primer hard enough to ignite it. You can overcome this by installing much stiffer spring so it slams the primer harder...but not recommended and not needed at all. Keep these things in mind..
Also has a .55" group which is 1 shot from EACH primer with the gold dot load. So 1 AR Match primer, 1 win, 1 pistol, 1 Fed GM, 1 CCI...and mixing like that is still about 1 MOA.
RIGHT ROW TOP RIGHT and MIDDLE:
Test groups using mixed primers...16 shots each...Top is 62 Gold dot, middle is 64 Game changer. All mixed primers...