i recently purchased this rifle which says wells 510 on the barrel. this gun is a monster and im trying to find some info as well as some ammo for it. its not like the other wells 510's ive seen and it weighs 15 lbs. any help would be greatly appreciated. i believe this to be a custom fred wells but have no paper work. this gun is something ive never seen before and had to have it. thanks for all your help in advance!!