Here is a little food for thought.Was a time the only scattergun I owned was a Win 97 Riot gun.So,when I was invited to pheasant hunt,I used it.It was a cylinder bore.I figured I just did not have a tool for long shots,so I was less concerned about pellet energy at long range,and more concerned about pattern density at modest ranges.I bought heavy 1 1/4 oz loads of 7 1/2 and was happy with the results.
These days,I use a 12 Berreta O/U and I can change tubes.Most of the time,I use 1 1/4 to 1 3/8 oz of 5's on pheasants( Skeet 1 and mod,usually)
If you are tightening up a small,dense pattern,and shoot precisely,5's will probably give you best distance.If you are shooting skeet or improved cylinder,get them a little closer with 6's.If they are holding point and you get to flush them, Skeet or IC and 7 1/2's works.
Balance choke,pattern density vs pellet energy,and range.(And,what your shotgun will pattern)