At my airgun club we hold an in-house competition with a twist.
It is benchrest 25 yards outdoor, using wadcutter flat head pellets using either .177 or .22. Using.22 the scores are marked on outer, and with .177 on inner rings.
For personal pride, I choose to use a springer, so currently shoot it with a Diana 56TH 177 producing 10ftlb (800 fps with 7g pellets) with a Sightron SII 36x42 scope.
I have sometimes witnessed the pellets' trajectory and believe it distorts during the last 5 yards, even in still conditions. I have tried several pellet weights and they all seem to jump about.
I suspect there's a balance between sufficient power to withstand the outdoor atmosphere, weighed against a wadcutter's inherent instability at that range. There is of course also a significant dollop of operator error...

My questions for the ballistically wise are:
1. Would a match rifle shooting at lower velocity say 550-700 fps calm the pellet down? A FWB 300s, FWB 600, or Anschütz 250 for example?
2. Should I give in from championing .177 spring or ssp and use a .22 pcp instead?