I've built four 223 bolt rifles over the past several years - two on new M700 SA from Brownells, another one on a Win M70 Stealth I purchased new several years before I bought my lathe and started doing my own bbl work, and the last on a Pierce TG action.
Starting with the M70 - I had a spare PacNor 1-7.5tw 4-groove sitting in the rack, so pulled the factory bbl and chambered it with a 223 Match reamer for bolt guns. It shot everything I put through it very well, up to & including JLK 80VLDs. Still had several partial boxes of JLK 90VLDs sitting around from shooting service rifle in NRA XC HP matches; got curious enough about how they'd shoot in the 7.5tw bbl to try them at 600. After years of shooting AR15 SRs with 1-6.5tw bbls (we were told the 90s needed that fast twist to work), I was very surprised to find that the JLK90s shot just fine out of the 7.5tw bbl. Chrono showed avg vel of around 2850fps with these N550 loads out of the 27" PacNor, and the best of them shot well under 1 MOA at 600 - nothing spectacular, but some of these bullets were out of a lot that Jimmy Knox brought to Perry in '03 that gave all sorts of problems out of our 1-6.5tw AR bbls.
Next project was a M700 with a 26" Krieger 1-7.7tw in a B&C A3 stock. It wouldn't stabilize either Berger or JLK 90s well enough to give good accuracy, but it sure did shoot H75AMaxes, S80MKs, & JLK80VLDs good. Sold it to a friend, only because I still had the M70 223, and was planning the next build - a 223 AI.
Bought another M700 from Brownells, and chambered a 26" 1-7tw Krieger for 223 AI. Put it in a McM A5 with R&D DBM, a TPS 20 MOA sloped rail & Vortex Viper PST 6-24x50. This thing beats all I've seen out of the 223 case. Not that it gets so much better velocity (it doesn't), but the accuracy with Berger 90VLDs (it also shoots the 90LRBTs really well - too bad they discontinued them) is perhaps better than any other 223 I've ever owned. It's shot several 5" 5-shot groups on steel IPSC targets at 1000yds, and allowed me to get hits on 1300 & 1400yd steel targets at a local precision rifle match, even though I ran out of elevation on the Vortex when dialing up from 1300 to 1400. I've heard a lot of guys talk here & on other forums about how picky the 90VLDs can be, but all I did was load them to max length for the AICS 10rd plastic mags, and they shoot lights-out. This rifle shoots consistently better than the last 223 I built, which is a Pierce TG action in an Eliseo R5 chassis with a 30" Bartlein 5R 1-7.2tw bbl, chambered with my 223 Match reamer, and throated out an additional .080" specifically for 90s.
