From the 16 yard line ...if you're getting on your targets the way you should, shooting them when they are still rising ( not when they are flattening out or dropping )....you'll be breaking them at about 35 - 40 yds from where you stand ( 16 yds) ....so a Modified choke is plenty. If I shoot Trap singles at the 21 - 23 yd lines I tighten up to an Imp Modified... and at 24 - 27 yds ( where I have no business shooting from - I go to a Full choke).
In terms of shells..../ for 16 yd Trap singles.... 7/8 oz or 1 oz of shot ...either in 9's, or 8's is plenty ...and at 1150 fps is fast enough..../ you don't need 1 1/8 oz of shot and you sure don't need anything at 1300 fps...
Having said that....my primary shell for many years in a 12ga ...has been 1 oz of 8's right around 1225 fps...and I use the same shell....for Trap singles from the 16 - or back to the 20 yd line, and Skeet, sporting clays or 5 stand...
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Briley is a solid company ...and I won't downgrade their assertions...but I don't think ported chokes make enough difference that I could ever tell ...
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I'm not a big time Trap shooter.....but when I shoot Trap, my primary gun, is a Citori XT Trap, a 10 lb O/U with 32" barrels, a Gra Coil system installed...and I use the Midas grade Browning extended chokes....so adding a ported screw in choke, wouldn't make much difference in my case.
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With the cost of shot going up all the time, I have transitioned most of my 12ga practice loads to 7/8 oz of 9's for Skeet...and I've been trying to work on a 3/4 oz load of 9's as well for skeet ...but I'm having trouble with the crimps / but the 7/8 oz loads of 9's or 8's break Trap singles very well / or at least well enough for me to average about a 94 out of 100. While scores like that won't win any tournaments ...its all I want out of my Trap shooting.
Just a note: but serious Trap shooters would threaten to sell their gun - if they averaged a 94.../ 98's or better are the norm for serious competitive Trap shooters.../ and for guys that shoot that well...yes, I will see many of them shooting Imp Mod or Full chokes.../ but the rest of us don't need chokes that tight to break Trap targets, in my view.
Barrel length ...doesn't affect the load or choke you should use / barrel length, affects the length of your sight plane...and swing characteristics. In Trap, where there isn't much right to left/ or left to righ -- barrel movement ...most of us want heavier and longer guns...so we can smooth out the follow thru / the gun maintains its momentum as you execute your shot better with a longer and heavier gun / where that Trap gun is too long and too heavy for effective all around shooting for Skeet or Sporting clays...where I go with an 8 1/2lb gun with 30" barrels..
But the gun you have is just fine.../ and lighten up on those shells...to reduce recoil and maybe get better patterns. If you don't have a Mod choke ...then shoot the IC ...and maybe go with a shell of 7.5's...instead of 8's or 9's..
...and he wouldn't want it any other way either.