Rechamber .223 for 5.56?

[bootsmcguire]

Just shoot 5.56 in it....you will be fine.

Probably, unless you have a 223 chamber with a tight/short free bore. If its too short, and ammo is too warm then bad things start happening.

Do like sharpshooter says and do a chamber cast. If the free bore approaches 5.56 levels then I'd go for it. If it's on the short side then I wouldn't and maybe have it lengthened.