I found this Bruce Buck article enlightening.
I and my regular shooting partner have an ongoing dispute over whether or not we should shoot 1 ounce or 1-1/8 ounce loads for 16 yard trap. His scores regularly drop by three kills if he shoots the lighter load and the other day I did much better shooting his high velocity 1-1/8's. This suggests that the high velocity (about 1350 fps and forget for the purpose of this post that the speed exceeds ATA limits) more shot is better.
Perhaps and perhaps not. My take on what Bruce is saying is that there is a differnce in lead between the two velocities, but not as great a realized difference as between a low velocity and a boomer. HOWEVER, if one's built in computer is used to calculating leads for one velocity, and you go to another the computer may be thrown off.
My buddy has been shooting his 1350 FPS for at least 6 months and I wonder if he lost so many birds more because he was giving leads appropriate for the faster load and not so much because of a less dense shot pattern (all were loaded with the same brand of #8).
As for moi, I had been shooting 1's for a coouple of weeks, then 7/8's for a couple, then back to 1's just for the first 3 boxes the day I tried the 1-18 high velocity loads for my 4th 25. The velocity of those 7/8's was 1250 fps, the ones were 1200. I was bewildered as to why with more shot, I was getting lower quality breaks than I got with the 7/8's.
While the additonal 50 fps in velocity may have had something to do with it, and the birds were bio, I am not thinking that the reduced speed translated to a need for a bit more lead and I was probably breaking clay with the periphery of the pattern. The boomer 1-1/8's reduced the need for any lead to center the pattern.
I am rambling. Does this make sense?
My primary conclusion from this is to stop jumping around from load to load.