My 10 year old will be going on his first turkey hunt in a couple weeks. He has a Rossi single shot 20 gauge with a modified choke barrell (not a screw in choke). It will shoot 3 or 2 3/4 shells. If any of you have shot a 20 with mod. choke, what shells worked well? What was the effective range? Obviously, I am going to pattern shoot the gun, but looking for some tips. Thanks!