I just spent about $300 on a broad ammo selection recently and only got one design that would shoot sub MOA.
The good old full wadcutter is accurate out to about 75 yards, then it seems to destabilize. It shoots a ragged hole at 50 yards.
I used the 148 grain H&G 50 design sized to .358. It's a seems like very popular design for 38 cowboy action shooters and a lot of casters make it in soft cast.
The Texan didn't seem to like the lighter stuff even with the power wheel on minimum. At 50 yards it would put up a 4 inch or so vertical string with 105 and lighter bullets and the JSB pellets. The medium weight stuff (105-140 grain) didn't do great at 50, around 2-2.5 inch groups. I got decent groups with a 140 grain HP boattail and 145 grain HP, 1.25 inch and 1.5 inch respectively.
If I had the knowledge before hand I would have only purchased 140 grain and above ammo to start the trials with....oh well hope this helps with the hunt.