UPDATE:
My outfitter insisted that all hunters range test their rifles before anyone went afield. They put a folded napkin on a piece of plywood and placed it at 50 yards. First shot out of the ProHunter put the 350gr FP squarely in the center of the napkin - no problem. Nikon red-dot worked fine. (Ultimately, all shot opportunities were from point blank to about 50 yards depending on the stand set-up.)
The lodge was nice but the hunting was poor. Very few hunters even saw a bear during the first few days. By Friday morning 7 hunters took only 2 bears. One was under 100lbs and the other was about 170lbs. The outfitter did not have a scale.
Oddly enough, he didn't skin bears either. A taxidermist estimated the weight of the second bear.
I had an average size bear come in to the bait around sunset but it never presented a decent shot. The bait was poorly set-up and the bear was smart enough to work the pail from behind while staying in the brush.
To answer a few posted questions:
The Katahdin barrel was cleaned every 20-30 rounds after break-in.
The barrel was not shot hot. It was actually difficult to get any heat to build up in this fat little barrel with the large bore diameter.
I used RE7, H335 and IMR 4198 with similar results. Most of the shooting was with the IMR 4198 @ various levels.
All bullets were crimped.
Switching to a 3x9 rifle scope did little to reduce group size. The red-dot was remounted for hunting.
I'll be heading out again in the fall and hope to get this rifle shooting < 2moa before that time.