Any 10m target rifle that's up to job should be OK for 20 yards indoors or outdoors in moderate wind conditions. A FWB 300s rifle would be up to the job, as would a number of other springers in it's class and the same also goes for PCP 10m target rifles. A member at our club put diopter sights on a HW100k scope rail a tunnel foresight on a barrel shroud to try 10m. What we didn't do was turn the power down but it worked well. I have an LP50 pistol that will easily group within the 10 ring of a 10m ISSF pistol target at 20 yards from a bench-rest and that's set at 5.5 foot pounds.

Power is not so much the issue, it's the quality of engineering and inherent accuracy of the gun.

Then you've got to do your bit

Hope whatever you try works well for you.

Cheers,

Mick