All 45-70 rifles that I am aware of will handle bullet weights from well under 400 gr up to 500 gr, which includes your H&R Buffalo classic. This being a single shot, cycling problems do not exist, but wanting to use the same bullet in your Marlin narrows your LBT LONG RANGE bullet option to the M, or Marlin profile, which in fact is about as good a long range bullet as can be had if bullet weight is around 500 gr. If you drive that weight to good hunting velocities, recoil will be severe in the Marlin, due to the heavy weight, but performance will be stunning out to ranges one doesn't normally consider 45-70 leverguns capable of
If chosen strictly for hunting the lever gun would be more satisfactory with a bullet weight closer to 400 gr so it could be shot at good hunting velocity with moderate recoil. By good hunting velocity with this bullet I consider 1800 fps top end, though the gun will push it to 2000 fps without getting dangerously close to bulging somewhere.
By all means try LBT lubricant if you are using smokeless powder. You'll never go back to anything else. For example, with alox the 400 gr/2000 fps speed I've mentioned above would cause severe pressure problems, the velocity limit being perhaps 200 fps less than with LBT lube. This with gas checked bullets. If you choose a plainbase, which would be fine for typical long range shooting with this cartridge, and perhaps required for many matches, as velocities are normally quite low, being limited by black powder.
If you intend to shoot black powder, be sure to specify that on your order and I'll cut extra grease grooves to accomodate it.
