my question is what is a accu. choke because i am going to use my uncles gun and want to know if i can change that to a full choke with out buying a new barrel.

accu chokes are Mossbergs choke tube system for some of their guns. they also have ulti-mag chokes for other guns. I'm certain that you can get accu or accu-mag chokes in different constrictions including full and super full turkey chokes if you look around. I don't have a mossberg, but I'd just make sure that any choke you get will fit the particular gun you have. If you do a google search for choke tubes for the gunyou have, you will see what's available.