The req'd bbl wall thickness differs, dropping the further forward/away from the front of the chamber the datum point is located - since the internal pressure generated by a fired cartridge is also dropping along the way.
Generally, at the muzzle of a 22" bbl, bbl wall thickness must be at least .121", making for a minimum muzzle OD of a .358" rifle .600". ( .121" + .121" = .358" = .600" )
Theaded holes in the length of the bbl generally should/usually have a screw tightened in them, re-inforcing the void - IOW, if the factory did it, fahgettaboutit.
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