223 is not the best caliber to shoot cast bullets with. At the speeds required for cast your range and energy will be limited by the bullet weight. The 223 pressure requires a hard alloy so bullets will turn to dust on hard targets and just pass though soft ones. 223 does best with heavier jacketed bullets. It can be and has been done but if I was buying a new rig to shoot cast with it wouldn't be a 223.
Something that uses 38/357, 44mag, 45colt, 30-30, or 45-70 are better choices for cast bullets. Most c/f bottle neck chamberings require down loading when using cast so heavier pills that don't go as fast make better cast bullet shooters. The 9mm PCCs shoot cast well. 45 acp is good also.
38, 45C/45acp, and 9mm don't need gas checks so are cheaper and easier to load for. 45 colt may be the best cast bullet shooter available but those 250-255 grain bullets can use up some lead pretty fast (bullet traps help keep cost down).
If you don't mind using GCs and moly lube the 357/44mag, 30-30, and even the 308Win with heavy bullets all work well with cast at normal fps loadings. There are many good cast bullet chamberings - I just named the more common ones. Anything you can shoot a 200grain bullet at 2000fps for 2000ft# of energy with works very well with cast (targets, hunting, or anthing else).
All that said - if I wanted a new bolt gun to shoot cast with, I might go with a 308 and cast 180 or 200 grain GC bullets for it. 6.5 Grendal or 300BO (if you can find either in a bolt gun) would be good choices also because they have lower velocities.
