Well, I guess I have learned to manage the 'crud ring' after all of these years. I shoot a lot of T7 just because of the price of BH.
I am basically shooting several different Knight ML's. Shooting T7 with percussion caps is not a problem at all, shooting T7, at the range or while hunting. Really no need for patching. With 209 primers, that can lead to a problem but really nothing insurmountable. I use the coolest primer I can, but still I am shooting W209's primers 99% of the time. I have in the past used ML 209 primers and really did not see/feel a significant difference.
The most significant difference for me is what I put/use in the bore. I have found that using non petroleum oils and products to be a really big factor. Yes, the 'crud ring' will form but not nearly to the extent as it might were there petroleum products in the barrel.
Shooting T7 at the range or for recreation I do patch after each shot. Not only am I allowing some cooling time for the barrel but it does slow me down also. While hunting and if it were needed I can shoot 4-5 shots before I feel the need to run a slightly damp Windex patch to clear the 'crud ring'.
Because I am using most 275+ grain projectiles, in my 50 cal. rifles, I really do not see a significant change in muzzle velocity with either powder.