The "Trapdoor Springfield" was available in both 45-70 and 50-70.
The Remington Rolling Block was also available in 44-77, 44-90, 50-70, and later, the 45-70.. ( a very popular caliber of the times.. )
Of course, the most famous of the buffalo guns was the Sharps Model 1874..
Sharps also made a 50-90 model, used by famous buffalo hunter Billy Dixon who took out an Indian warrior at 1,500 yards. (.85225 miles )
Other makers were Ballard, Maynard, and Spencer. ( which was also considered and exceptional gun..)
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I have read an article (or ad) recently concerning 45/70 and 45/110 lever-actions..
They are readily available in the modern market..
Reason for interest was the recent talk of "outlawing" 50 cal rifles in CA..
I figured one way to get around it was to simply go to the 45/70..
I am sure that the 50 cal of today is better than that of yesteryear..
That, however, wasn't the point.. In fact, it proves my point..
If a powder and ball 50 cal. ( or 45/70) was powerful enough for Bison and Grizzly in the 1860's and 70's, today's models are more than sufficient..