DAA, I tested my loads with the only choke I had for my Browning Gold. "Hawglips" over on Gobbler Nation recommended I try a more open choke. That might have improved my patterns. I have been shotgunning predators since 1964 on a fairly steady basis. TSS just flies in the face of accepted choke concepts. Mod to ImpMod seems to work the best. Hawglips is pretty much the guru on TSS shotgunning.
I have done a lot of TSS load testing in 28ga also. I even shot one coyote at 53yds with 1oz of #6TSS. He just flopped over. That was that. Best choke for the one ounce load in the 28ga was ImpMod. 1oz #6TSS=139 pellets. I only pattern tested to 40yds. 63pellets in 10", 10"to20" 57 pellets. That is 120 pellets in a 20" circle. 86%. The shotgun was a Beretta 28ga 687 SP3 over/under, 30" bbls. Tried the same load in my Beretta A400 Xplor 28ga, 28" barrel. Pretty much same results.
I pretty much stopped patterning when funding grew shallow. $50 bucks a pound is costly. I did not add buffering to any of my TSS loads. My logic; TSS does not deform in firing.
A few years back you did an outstanding series of articles on the 20/250. At that time a friend and I were running the 20/250AI in Nesika rifles. 50gr Berger bullet at 3950fps. Flat to forever. I retired mine three years ago. Bullets started arriving other than point on. How did your rifle turn out for you?
Carl L.