So, I ended up with his “long range” air rifle and there is no way. I couldn’t get it to group at 100yds. I’m glad I rescued the rifle, as it is a rare piece in the airgun world… but I didn’t have all the info back then on FF. Sorry to the OP, just had to say this.
The panthera is a great gun, I have the 500mm and I’m going to move on from it to get more into rimfire. But it shoots MOA at 100yds, no problem. Looks like you got a shooter for sure!