It is necessary to pull the hammer all the way to full cock before lowering it. If you pull it to half cock and load the gun, do not simply let the hammer down from there, it will not properly reset the bolt. You must pull the hammer to full cock before lowering the hammer, either to an empty chamber or a safety pin.
This is true of any Colt Single Action, cartridge or caplock, but the gun's timing affects the severity of the problem, as some individual guns hardly are affected by failing to full cock them, others will freeze solid every time, but locking up does not mean your gun is mis-timed and needs work, likely as not that a gun that does NOT lock up from half-cock may be the one that has bad timing.
Treso nipples I believe require #11 caps, (sometimes CCI #11 and Remington #10 will fit about the same) so if you are using #10s they may be too tight, but you have to try both to see what works.
SASS rules require you to seat caps with a wood stick, never the hammer. Seating with a wood stick is not dangerous as long as you push slowly and steadily, do not strike., and DO NOT EVER use your thumb to hard seat a cap, as if it DOES go off it will drive the cap right into or through your thumb. Someone had photos on the internet once of such a damaged thumb.
