Alrighty I got an AR15 put together in 9mm. Friend gifted me a 3" Orion barrel which has 1:10 twist, have not slugged it yet. I put a 3X nikon P223 scope on it just to get an idea how the whole rig shoots. At 25 yards with Federal 115 grain it seems to group 2" or under. It is REALLY windy here today with some aggressive gusts
. This shooting today is from as benchrest a position as you can get out of this rig. I'm using Mean Endomags which are a 9mm conversion assembly that fits inside a 5.56 MagPul Pmag. Not that it matters a whole lot but I have a Brownells branded bolt in there and a Brownells branded 9mm buffer.
I backed up to 75 yards and shot a group with the Federal 115 grain that was not terrible, probably all on an 8-1/2 x 11 sheet of paper, then I shot a 10 round group with the Lee 120 TC bullet that was PC with TIGER DRYLAQ Gentian Blue baked at 400F-405F for 25 minutes in convection Oster toaster oven.
Load is 4.0 Alliant Sport Pistol, WW small Pistol Primer, taper crimped to remove flare only.
10 shot group at 75 yards, 7-3/4" for 10 rounds 6" for the best 9 of ten
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I'm pretty happy with that for first recipe out of the bag really, the 120 TC may not be the best feeding combination in this gun.