[T. O'Heir]

You're not going to get 3000 ft-lbs of ME with any handgun cartridge chambered lever action.
600 ft-lbs is well below the standard ME for large game like deer too.
"...165 gr bullet at 3000 fps yields 3000 ft lbs..." Nonsense. A 165 at ~ 2800 FPS runs about 1500 ft-lbs. Another 200ish FPS will not double the energy.
A 350 grain .458 Win Mag at 2470 FPS will give you 3065 ft-lbs at 100 yards.
A 300 grain .45-70 with an MV of 1810 FPS, out of a 24" barrel gives 625 ft-lbs at 400 yards. It drops 115.7" at 400 too.
A 240 grain .444 Marlin at 2350 FPS gives 630 ft-lbs at 300 yards. Drops 37.8" when sighted in at 100.
A 125 grain .30-06 at 3140 FPS will give you 706 ft-lbs at 500 yards. Mind you, sighted in 1.5" high at 100, it'll be -47.6" low.
a 750 grain .50 BMG won't be found in a lever action, but Hornady's Match ammo at 2820 FPS MV gives 13241 ft-lbs of ME. A measly 9403 ft-lbs at 500 yards and nearly a yard low.