Lets start with gas checked bullets and velocity capability. 2000 fps is loafing speeds if LBT lube is used, even with soft bullets, i.e. air cooled wheel weight metal.
I reccomend a 320 gr LFN without crimp groove for your rifle, if you want a heavy weight and intend to push it pretty hard. It won't stabilize well at longer ranges if you shoot them at lower velocities, like perhaps 1400 fps and less. If you like to plink, or hunt with lower velocity loads, a 280 gr is the best choice, and with any weight LFN in 44 caliber, 1400 fps will anchor most deer in their tracks. In other words, adaquate power with pleasant recoil. A 300 gr at 1800-1900 will get uncomfortable with recoil, and heavier bullets with more power is worse. The rifle is probably stronger and more capable of dishing out recoil than most shooters are willing to take. I shot one with my 280 gr WFN driven at 2450 fps, and the gun showed no signs of strain.
The reason I said no crimp is because best accuracy will be obtained from individual rifles if the bullet is seated out so it comes close to the rifling. A crimp can then be applied with the Lee factory crimp die, to prevent recoil from driving bullets deeper into the case. If you want to use the same bullet in revolver ammo, order the mold with crimp groove, try it and if it shoots well enough to make you happy (it probably will) use the bullet with that seating depth. Or, play with seating depth until optimum performance is obtained and crimp with the Lee die.