To add just a bit to Dennis' excellent advice I will say that even on those guns which do depend on the forend to activate the cocking mechanism there is the possibility of the pin protrusion being different with the barrels on or off so this is still good advice either way. It occurs to me a good method might well be to measure the distance down to the pins with gun fully assembled but un-cocked, then cock the gun & measure down to the breech face which would show actual pin protrusion.
On the majority of guns which do utilize the forend then Dennis's method would certainly still be great advice to determine what affect the forend has on the protrusion. I had not really thought about this aspect before Dennis, thanks for the tip. Had always just depended on measuring with the barrels off.
