Got the barrel on today. Thanks for the suggestion, Jim, but no light hammering was required. I tightened it up and backed it off about 4 times, each time as far as I could reasonably get without yanking on it. This got me to within 1/8 of an inch, and the next iteration I pulled just a bit harder and it all lined up perfect.
Mailman brought me new Remington a3 bolt today from chuck, with handle beautifully worked. It's quite "new" in that I don't think it has never been fit. My receiver was polished and blued, and a well worn bolt glides like butter. This one is very tight. I lightly stoned the cam surfaces to smooth up any burrs and roughness, but only just enough to knock the finish back. This removed the "grittiness" in opening/closing the bolt and made it smooth, but still very tight. So, following the TM to fit this new bolt, I need "COMPOUND, valve grinding, fine (SNL K-2)".
Can anyone point me to an equivalent? None of the ones I can fine have a grit labeled. I have 220 wheeler I use for lapping rings, but that is likely too coarse. One automotive forum I read listed 220 as "fine".
I've also got plenty of room behind the safety lug, so I plan to also lap the lugs before finish reaming and setting the final headspace.
EDIT: Larry Mr. Potterfield likes 600 grit, I suppose this is good enough for me.