I have a former .222 M700 BDL rechambered to 223. Amands in Faribalt MN rechambered it, I specified a chamber for military ammo and it has a fair amount of freebore besides. 1X14 twist, of course.
The first thing I noticed was the Hornaday 50 SX's were inaccurate, where they were the best before rechambering. Then I chronographed the loads and was getting an honest 3350 out of a 223 with 50 grain Hornaday 50 spire points. This combination wasn't "quite" as accurate as the 222 loads but certainly good hunting loads.
The rifle likes the 40 gr VMax best of all. Little-fingernail size groups from the bench at 100 yds. Certainly minute of woodchuck or prairie dog. It's good out to 300, where the 222 was just not up to it, in my opinion. The 223 seems to have more power and I like it better.
I'll have to rebarrel this rifle soon, probably 223 and I am thinking 1X14 twist. If I tried to get all the woodchucks and prairie dogs I've killed with this rifle into a wagon box, it'd overflow.