i dont have the stock barrel. i used a Flasc TM7 barrel with suppressor on the end because thats all i had. the barrel has a .690 bore size and i was using Inka Silver paint. shots could have been a little bit straighter but i'm not sure if its because of the barrel length, old paint, lower then standard velocity or just all 3.
here is the setup i used but with a smaller steel tank instead