I've had a .45 Texan SS for a month or a bit more now. Here's a few things I've found:
1) Watch for clipping in your shroud. Both my .45 SS and my .308 SS have had issues with one baffle clipping. In the .308's case, the baffle was drilled a bit off center. I fixed it by simply opening up that off center hole. In the case of the .45 SS, the first baffle is smaller from the factory than the other baffles and shaped differently. I had to open it up significantly. Once I did so, I started getting tighter groups with a bunch of different kinds of ammo. Before opening up the first baffle, I only got good groups with heavy ammo.
2) Mine can shoot 220 grain ammo in the 880s fps. My initial chrony results were lower than factory specs, but then I discovered my chrony was worn out from several falls over the years. Changing chronies put my numbers where Airforce says they should be. The tightest shooting ammo in mine is Nielsen 290s. With the bad chrony, they were flying 720. I suspect they're really doing about 800fps or so. But I have decent results with the lighter NSAs now that my clipping problem is solved. To my mind, if I can have my ammo of choice shoot 850 or better, that's plenty of power and velocity for at least to 50 yards, which is the max I'd take game with it simply for trajectory's sake. For myself, I'm not considering the upgrade kit simply because I presume that the extra power may make the gun too loud for my tastes.
3) It shoots Hornady round ball .457 well and is therefore a good plinking round. NOE is about to release a .45 pellet mold that may be a good ammo choice for this gun for higher shot count and max velocity.