Straight Walled, Rimmed .45 caliber rifle cartridge
.45 is the (approximate) diameter of the rifle bore for the caliber cited (in inches). -70 refers to the black powder charge used in the cartridge as originally designed.
Originally created for the US Military shortly after the civil war, the .45-70 is also called the .45-70 Government. Using modern powders in modern guns, the .45-70 is capable of propelling a 300 grain bullet at over 2200 feet per second for a muzzle energy of about 3500 lb/ft. It can use bullets exceeding 500 grains and varying powder loads to accommodate many different situations. It is capable of humanely and safely taking any large game in North America and is an extremely versatile and capable defensive load.
For comparison, the 5.56 Nato cartridge used by the military today in the M16 rifle (and variants) is either the M193 which propels a 55 grain bullet at a bit over 3200 feet per second for a muzzle energy of about 1300 lb/ft or the M855 which is a 62 grain bullet moving 3150 feet per second for a muzzle energy of 1370 lb/ft.
The venerable .45-70 is a versatile and very powerful cartridge.