I’ve had problems with lot-to-lot consistency with the Hornady 55gr SPT w/cannelure.
I suggest it’s the bullets.
TAC is a well known and proven powder in the .223. 23.5gr is a good load.
Most AR chambers are as you describe. My RRA NM AR15 with a Wilson 1/8” Wilde chamber requires the 80gr Sierra MK to be seated to 2.555” to touch the lands. It’s 1/2 MOA at 600yds. It’s under 1moa with a 75gr Hornady BTHP match bullet at magazine depth (2.25”).
I have a Dpms Sportical barrel in a CMMG narrow free float tube that is also under 1moa. However with the latest batch of Hornady 55gr BTSP w/cannelure, all the rifles shoot them 1.7-2moa.
It’s the cannelures that screw up the bullets. I’ve seen non-cannelure 55’s shoot in the .3’s from my Rem M700 .22-250 at 3,700fps.
I seat them about .001” short of the cannelures. No crimp.
However, for the AR’s I ALWAYS FULL LENGTH SIZE !!!
Failure to fls can cause a slam fire, or out-of-battery discharge. I’ve seen both happen.