RST offers a 2 3/4" 1 1/4 oz pheasant load in its Premium Grade line. 1200 fps. You can get them in size 4, 5, or 6 shot. I've used some of those, and I think they're as good as any equivalent load on the market. Price I have listed is $12/box. Even with shipping, those will cost you less per box than the "premier" loads from the big ammo makers. And the RST's, with much less velocity, also produce much less recoil.

They don't list pressure, but I'm pretty sure they'll tell you if you ask.

Re tower shoots: They're designed to more or less simulate driven shooting. The loads I've shot when in Scotland have been either 1 oz or 1 1/16 oz. And they'll do the job quite nicely on birds under 40 yards. And a 40 yard driven bird is pretty darned "tall" at your typical driven shoot. Not speaking of the places that specialize in really high birds, 50 yards and more. But those guys shoot heavy, long-barreled guns pushing heavy loads through tight-choked barrels.

We Yanks are used to shooting walked up pheasants over dogs (unless you're a blocker) at mostly going away angles. They're a lot harder to kill when they're shot as outgoers than they are as incomers. Coming at you, their vitals are far more exposed. So those light British loads, which are mostly Brit 6's (slightly larger than US 7's) do the job very nicely. You've also got a bunch of "pickers" lined up behind you to collect the victims and to run down the cripples with their dogs. Usually retrievers and spaniels.