Smoothbores are now allowed in NY so i was wondering , could i buy a single shot cap lock 12 guage shotgun for smallgame and then use it for deer come deer season. I believe it probibly would be 72 cal. or larger, but why not. I am not concerned with range as the max range would be around 50 yds.

Yes, it works. There are many of us using Brown Bess muskets, .75 cal, with RB for deer. Same, same except for ignition. GREAT fun.