Scoot....I have 3 rifles in 223. Two are AR15 bushys, one is a Rem m700Lite Varmint Stainless Fluted w a 22" barrel. The bushy I shoot most often is a DCM, 20". The Bushy has a 1-9 twist, the Rem has a 1-12 twist. The Rem shoots 40-55gr bullets into dime sized groups with great regularity. However, I tried the Hornady 68gr Match HP and they actually keyholed!!!
The Bushy shoots 55gr bullets into about an inch or less and, 68gr Hornady match bullets into dime sized groups over and over again. So...what exactly are you going to do with the rifle...punch paper(as I do w the bushy) or varmint hunt where a 50-55gr bullets are just fine to 300 yards.
BTW...I had a hankering to use the Rem on exotic sheep at a NE preserve where there are several 300-500 acre open fields and shots could get long! I wanted to use 60gr Nosler partitions. I could NOT get any kind of accuracy from my Remington at all. 2-3" groups at 100 yards. I actually settled on using an 06 (pics etc posted in the exotics forum).
So...If I was going to have another 223 built, I'd first decide what I was going to do with it. I'd also suggest the 1-9 for versatility and if a truly dedicated varmint gun, I'd go with the 1-12 and shoot lite for caliber bullets. Hard to go wrong with either. BTW...each is set up with Timney triggers and 6.5-18 Leupold VXII scopes.