Just out of curiosity, why is 3 shots of .44 Mag in an inch not good enough??
You have a carbine sporter and those are not intended to be benchrest or match guns consistent with long shot strings.
This is easy enough to check. Fire your three shots close together, and then take a "coffee break" and return to shooting when the rifle is again cold. Then see where shot #4 goes. If it goes into the same tight group the earlier shots did, then there's a good case for heat being the cause of the flyer.
You have a carbine sporter and those are not intended to be benchrest or match guns consistent with long shot strings.
I don't agree with heat.
This is easy enough to check. Fire your three shots close together, and then take a "coffee break" and return to shooting when the rifle is again cold. Then see where shot #4 goes. If it goes into the same tight group the earlier shots did, then there's a good case for heat being the cause of the flyer.