Tim,
I did exactly that during the last NEFTA winter league. I went round with the .177 RB2 Airsporter that is now in the safe custody of Gareth W-B. On a day where the vast majority were struggling to break 20 ex 30, (IIRC top score was no more than 25) I put in an 8ex30 with the airsporter (no scope fitted) after I'd put in 19/20 with my full blown FT rig. It was damned good fun doing it too!