Are you using FL bushing dies or FL dies with an expander button? I would assume that since you are into rifle match you are using bushing dies. I think that people need to make that disctinction when they talk about FL sizing.
I shot a 223 NM AR15 barrel out with a standard Lee Sizing Die. My 223 and 308 Lee dies give me 0.001” case neck run out and I think that is pretty good. However the Lee Die does not reduce cases as much as a small base die, as evidenced by this case that won’t drop all the way into the reamer cut case gage.
This Redding Die I will use when the RCBS small base die I used to size this case wears out. If you notice this case was reduced enough to drop all the way in.
I have buds who are outstanding shooters, and two are National F Class champs, and some play with bushing dies, some don’t. I am not good enough of a shot at 1000 yards that neck bushing versus standard sizing die makes a difference on target. What I have observed, is the ability to hold your rifle consistently each shot, a consistent trigger pull, and being spot on with your wind call, makes for smaller groups than super duper reloading equipment. Many times I have had the wind blow my round three feet left, or three feet right, and neck sizing, bushings, or standard sizing dies techniques won’t fix that issue.
After three years of shooting competition small bore prone, at least once a month, more often twice a month, and shooting at the Nationals, with a hand held rifle I am occasionally (v. Occasionally!) getting 50 yard targets that look like this, but three years ago, I would be shooting 47’s, 48’s with a couple of X’s. It takes work at the range to shoot well. Poor shooting skills cannot be compensated for with esoteric reloading techniques.