Ok, range report:
Short version... I'm a happy camper.
Longer version... was in quite a rush to the range and back, it was crowded, I was rushed by fellow shooters, benches were less than ideal, it was off/on gusty, and around 70F, and despite all this the gun already shoots better than the returned one.
Best 3 shot group so far is 0.75" at 100 yards, with 70 gr by weight of BH209 and 44 cal 300 gr XTPs.
Only a dozen shots so far, but had to be quick today... so didn't give the barrel much time to cool (5 min) between shots. Loading this barrel also feels a lot more consistent than the previous. Before it felt like pushing a wad past a full choke in a shotgun, then easy the rest of he way; this gun takes an even amount of pressure to push a bullet and sabot from the muzzle all the way to seated.
I suspect I'll find this barrel to be more accurate overall than what I had.
Thanks for all the tips provided so far, they'll likely help me tune some good loads with this one.