I use T7 almost exclusivley. Have for years. It beats pyrodex hands down.
The stuff is a fast-hot burning "sporting grade" powder, the 3f you have is a little hot for the .50 cal, if you can, take it back and get some 2f/ffg, if not don't fret you can use it, just drop the charge a bit more.
T7 loads need to be cut back from BP recomended loads by 10/15% for best preformance.
In my son's .50, we use 55grns of T7 ffg under a .490 ball with a .020 cut at the muzzle denum patch. The patch is lubed kinda on the dry side so, we also swab between each shot with a spit patch, once down and back too keep the bore fouling consistant. Bore swabbing is a point of contetion, even with black, it's something I do but others don't. That load is a winning load for that gun.
If you use prelubed patches, a .015-.018 thickness should be about right, then just work the load in 5 grain increments up or down until you find the best load for you and your gun. No less than 45 grns unless your just knocking cans over and no need for any more than 80. 80 is plenty for killing deer size game out too and inside 100yrds. You may find it likes .495 ball better.
Your gonna hear about the "crud ring" T7 leaves, it's true, near the seating point of the prb, when cleaning you'll feel the jag drag across something, it's some kind of build up left from igniton and will clean out and also causes no harm.
You'll still need to clean the gun right away after shooting like you do with black, as there are some "salt's" left from the powder residue that will start rust.
Another issue I have noticed with the end of the can stuff, is it tend's to settle and you'll get finnings at the bottom that WILL change the volume charge a bit to a hotter load.
Good luck, the stuff works great, It's just another learning curve.
