RE: CVA Mountain Stalker
Must be some friend to just give you a gun. Wish i had friends like that.
Anyway start with powder charges measured to the same cal. as the gun. ie 50 cal gun starts with 50 grains powder. Increase by increments of 5 grains till the groups fall apart.
The bullet question is tougher. Just like centerfires some guns just like certain bullets and wont shoot others, Afraid the answer there is trial and error. But thats the fun part anyway shooting and figuring this stuff out. Round balls with light powder charges will surprise you!(at reasonable ranges)
If the gun is older ,and i think the stalker line is, it will be the number 11 caps for ignition. I like to use Hot Shot nipples because the flash hole is a bit larger for more reliable ignition. While shooting I like to do a hasty cleaning every 3rd shot. solvent patch followed by one soaked in alcohol then dry patches. Keeps loading easier since it cut down on crud in the barrel. This works for me you may experiment a bit and find something ya like better.
Dont forget accesories like bullet pullers and patch pullers youll never know frustration till ya have a misfire in the field and forget your bullet puller!!!
The best guys for info on here are Cayugad and Triple Seven. I never seen them give a bad bit of advice and I've learned quite a bit from both.
Good luck!