Fer me it would be the Winchester 30-30 model 94 "the gun that Won the West" great brush gun and well I just like it 
throw in some 170 grn and go a huntin', or a killin' 
Won the west....I thought that was the Sharps 45-70 Government. It's what 90% or more of the folks took west with them in the late 1800's.
The 30-30( it means 30 Caliber 30 Grains black power) was not available till the turn of century. The 45-70 is a 45 Caliber round on top of 70 Grains of black power, and is a harder hitting round then the 30-30, with better range.
So with that said I would have to say one of the transition guns, a 303 British Lee Enfield Number4 MRk 1 *( Black power, Cordite{the stuff they use in cannons}, Smokeless power), 8mm Mauser(same loading options), or a Sharps 45-70( only black powder or smokeless replacement) They are easy to use, reload, and can all be used at longer ranges 1000 to 1800 meters.
