I've had a good experience moving into use cast in the AR, thanks to a lot of good information spread out in numerous threads on the site. Thanks to all of you!
I'm shooting an S&W M&P 15 Sport II in 5.56 NATO with a Surefire Pro Comp muzzle brake and 3 MOA Truglo red dot The first 1000 rounds have been factory Winchester 5.56 NATO with 55 grain FMJ or my reloads using Hornady 55 grain FMJ BT over H335. I ordered in the Lee 225-55-RF, some Hornady checks and after slugging the throat a .225 H&I sizing die for the Lyman 4500. I went the route of H4895, starting at 20.4 grains, no filler, CCO SR Primers and seated the bullets to 2.096 OAL. They were lubed with White Label lube. Bullets were COWW + 2-3% tin, visual then weight sorted to 55.0-55.1 grains, age hardened for 2-3 weeks while waiting on a few things. I'd started at 19 grains for 5 rounds, which cycled the action but you could tell it was a little slow and had 1 of 5 rounds that didn't feed properly. The next were at 20 grains and they cycled the action fine. Seat of the pants on some gongs at 35-45 yards was good so I loaded up some in mixed brass, all of which were prepped by deburring the flash hole, cutting the pockets to uniform depth with the RCBS tool and trimming the brass to 1.750. An RCBS 5.56 NATO SB die set was used in addition to Lee's collet crimp die and an NOE M type expander for use with Lee's Universal Expander die body.
I set the target at 50 yards and rested the front of the rifle only on a shooting bag. Here's the group along with chronograph numbers, which measured about 2.3 inches. I think I need to go back now, sort the brass for more shots and put something a little more accurate on the rifle optics wise and I expect it will do better. Maybe 100 yards this weekend. I'm pleased so far.