The reason I don't use T7 was etched in my brain years ago. I did a lot of testing on the P and the T7. At that time I was just starting to paper patched bullets. Up to then I was using pyrodex RS. My 45 was hang firing real bad so I tried the P so it would settle into the snail better and that worked. This day I was shooting my 50. I was out at the range and a buddy of mine was there to shoot his white mountain carbine 50. I was shooting 80 grains of P and the T7 I don't remember the load, But I worked up the grains on the T7 so I had the same FPS. I think I used less T7 to get to where the P was but I don't remember now.

Anyway, my groups showed a real liking for the P and I was done testing. In my testing on my rifle with the paper patched bullets, I found that if I went much over 1300 FPS my 460 gr bullets were not grouping reliably. So staying in that 1300 FPS range was the target.

My buddy wanted to speed test the white mountain carbine. He was not familiar with the T7 and loaded 90 grains, the same as he used of RS. He touched it off and the stock cracked.
Now that stock cracking may have been a fluke. I know that he is not the kind of guy to over tighten the lock screw. His velocity with that short barrel was 1400 if I remember right.

Between that and the fact that the T7 didn't accomplish the same groups as the P did at the same velocity was the reason I stayed with the P.
Now since that first try with the T7 I did end up hardening my lead a bit. I was using pure and now I am using lead that is between 6 and 7 BHN. I do wonder how that would affect the T7 groups.
The last thing I do remember between the two was the "crud" ring left by the T7. I do remember that being another factor with my paper patched bullets. Yes the P does have a crud ring but I can work with it.