Measured some 222 and my 6mm. Diameters of both size receivers are
1.325" (or so). Bolt body length is 5.165 for 222 and 5.480 for 6mm.Bolt diameters are the same at .700
I found that the Canjar trigger on my 6mm does work, safety wise. My Dad will probably get a Timney for his 222.
The idea of a 6.8mm SPC on the .222 action is interesting. The boltface is a bit wider than the 222, time to look for any available 788 bolt bodies... Unobtanium most likely...