I have a Pietta 1858 Remington Army and Remington No. 10 caps fit great.
I also have a Uberti Whitneyville Dragoon and a Pietta 1860 Army and the No. 10 caps will fall right off if you invert the gun. I've also tried No. 11 caps. The nipples look in okay shape to my newbie eye. Is there...
