That would be .0025" per side, yep lots of leading.

The bullet should be sized .001" under bore diameter.

Not .045" per side but .045" of total constriction.

The design requires the proper hardness of the projectile and the deep bite of the ratchet style rifling in order the grab and spin the projectile.

Quite a bit has been written about loading for the 1050 and the 1250 fps loading. I once owned a 1550 fps Super Magnum Paradox gun....that was beast to manage the recoil in an 8&1/4lb gun.