Just received my set of extended chokes form CZ for my Canvasback. The gun came with two flush fitting chokes; according to the ID markings in the CZ manual, Mod is in the top and Imp Cyl in the bottom barrel. At the trap range last week, I was shooting my bottom barrel first. I wasn't paying too much attention to which barrel I was scoring better with...scores of 15-17/25 doesn't exactly lend itself to correlating statistics . I only shot once at every clay. I did find that, rather than trying to acquire and get the target quickly, I seemed to have a little better luck delaying just a bit. Being very new to trap, I'm not sure if that's the best technique or not, but it would seem that I'd want to perhaps put the Imp Mod in the bottom and Full in the top to keep energy and grouping a bit tighter further out... right? Lastly, changing out the ones that came with the gun with the new ones, I realized how dirty the area between the barrel and the choke OD is...I did not pull the chokes when I cleaned the gun. I think I know the answer now, but I'll ask anyway just to give the seasoned guys on the forum an eye-level slow one to hammer .... always removed the chokes when you clean, right?