The toggle link design just doesn't have the strength of later designs like the 1892.
Handsome guns though. I shot one in .44 WCF. Very smooth action, effortless really. The top ejection was rather weak, but worked reliably. Good for the handloader, you don't have to look far for your brass.
With the elevator design 1866's and 1873's receivers are about three inches longer and heavier than more modern designs.
Also the elevator design requires cartridge length to be within a narrow window. No long SWC's or short .38's.
The Italian replicas have good reputations amongst the cowboy crowd.