Bruce, both the M1 and M2 used two piece bolts and are outwardly similar. Internally, inside the front halves, the firing pins are totally different. In the M1 the striker is basically cylindrical with the firing pin itself offset to hit the rim of the .22 cartridge. The cavity in the bolt head in which that striker rides is centrally located and as such would be a piece of cake to convert to centerfire- weld shut the hole in the bolt face and re-drill one centrally, and reconfigure the striker/firing pin accordingly. The M2 on the other hand is a different breed of cat internally. In it the striker/firing pin is offset to hit the cartridge rim, and the cavity in the bolt head in which it rides is offset too. Therein lies the conundrum- how to fill that cavity so as to allow a new cavity be bored on center. M2 bolts abound, sort of, but aren't particularly cheap. M1 bolts are nonexistent- when they made the switch at the Armory, all M1's that were turned in got re-fitted with M2 bolts and all M1 bolts were scrapped. One may turn up- you know how that goes- but I'm not going to waste a lot of time looking for one because it's pretty fruitless.
I wouldn't even begin to try to convert an '03 bolt- it could be done I guess, but OMG the work involved would put the project right out of the "fun challenge" category into the "what the hell was I thinking, screw this I'm gonna go have a beer" category.
Sorry, fellas, to drive the topic off into the weeds a bit. Carry on.
