I personally, conducted my own tests on the same gun, lengthening one barrel's cone and leaving the other. The first test was standard forcing cone vs. a 1 1/2" long cone. I felt no recoil difference, but did see a decernable difference in pattern around the edges. The "flyers" were less and the pattern bprder more defined. Some might say it had the effect of making the pattern smaller. I say it reduced the damaged shot that created the edge irregularity. Either way, it wasn't my imagination. Next, I cut the standard cone to a 4" long cone and compared it to the 1 1/2" cone. I could see little difference. There might have been some slight improvement in pattern edge quality, but it was inconclusive to me, since I didn't do quantitative analysis nor a statistical sample of shots fired.
Me? I could not tell any recoil drop from a longer cone. I think many modern clays guns have longer cones than a early gun or SAAMI spec chamber and won't benefit. My K80 had longer cones than a SAAMI chamber. I do believe it matters in pattern quality from my testing. If the guys above have tested more thoroughly than I and have a different opinion, so be it. Until I see something to convince me otherwise, I believe it helps the pattern.
