I thought somewhere I read or saw it was a 1894 30 30.
Correction, it is supposed to be an 1892 44 40, but the bullets he is carrying look way too long.
Yep, it was all for Hollywood "optics." I don't remember if McQueen's rifle was a .44-40 or maybe a .38-40. Maybe, just maybe, it might have been a .32-20, but that's a guess. Whatever, it shot the five-in-one blanks used in all western pistols and lever '92 rifles. I haven't watched the show in many years but I do not recall seeing McQueen ever trying to load a .45-70 into his rifle.
L.W.