[Jbar4Ranch]

Of my 34 modern .44-40's, all but one slugged .429", give or take half a thousandth. One, a Navy Arms imported Uberti 1875 Remington, measures about .4315". In all fairness, I've never pulled a factory .44-40 bullet and mic'd it, so they could very well be .427", I suppose.

Ruger did a really weird thing with the .38-40's they made for Lipsey's, and no one really has a definitive answer why. They used a proper forty cal barrel, but made the chamber mouths way undersize at about .396". One story I've heard is the only jacketed factory ammo available at the time was a Winchester offering that used a .396" bullet, so that's how they cut the cylinders. Who knows.