+1 on going the 444M route. I have set up three of them in the last year and all are MOA guns @ 100 yards with cast gas checked lead. All three are of Illion, NY manufacture with extractors. I only slugged the first barrel and I got .4295". I am shooting .430" Lyman devastor HPGCs, with an as cast weight of around 270 grains, .430" 310 grain Oregon Trail True Cast WNFPGCs and 355 grain BTB @ .432". All do very well at velocities from 1,500 to 1,850 FPS, using I3031, H4895 or I4350. I have not tried to push these bullets to maximum velocity. It would be very easy, if you reload, to slow these down to 44 Mag velocities.
BB