Skeet is a game of Shoot Off's. At the top, you don't win a Skeet comp with 100 straight. You win it with 100 straight, then 25 straight, then doubles on 3,4 and 5, then another 25 straight, then more doubles...
So it really is all about the numbers.
That means the MOST effective pattern you can get. Which translates as a fairly open choke (not too open and certainly not true cylinder) with as many god damn pellets in it you can get.
As for "fringe pellet count", well most chokes wont give you that...many have very hot centres with fewer pellets on the fringes...with 7.5's...fewer still.
There are absolutely no ballistic or technical advantages to using anything other than a 9 or 9.5 shot size at all...none.
Ideally, for skeet, steel 9's are the absolute best cartridge...635 pellets in a 28g.
As for tighter chokes...I have used my U2's...I got great kills. If it was a totally windless day and I was on form, I might use them again.
If you have a good day and you are 75 straight, using 1/4 choke and 7.5's...feeling good! High and Low 1 go the same way...balls of soot.
But...come the doubles, the wind has got up...high one didn't break quite as well because the clay was a bit slower into the wind...Low 1 however is going like the clappers and dropping like a stone. You looked at the bad break on the high bird for a touch too long, swung round, low 1 is passing you by at 10 yards...how big is your pattern at 10 yards with 1/4 choke and 7.5s? Not big enough, because you have rushed and stabbed and ...missed.
So...now you are pissed and unless you can get a grip on that and the increasing wind...that wont be the only one you miss.
Unless you are a former Olympic Gold Medallist or a VERY experienced Skeet shooter...don't use tight chokes and do use 9's
I will use GB Super Steel if I have to, but ideally GB White Gold pro Steel.
@ Harley. GB do Super Steel Lite, which is a 21g steel cart. Possibly only available in 7.5, but as it is steel, you get more pellets so this should be OK..
They also do Super Steel 24g Fibre. I think you should try a box of 24g, because I think you would barely notice recoil with the ISIS.