Ran some shots over the chrono today, it was dieseling quite bad at first and was doing over 420fps initially.

After it settled down I got this string, looks pretty consistent I think?

Pellets were RWS Superdome .22

396.2
394.8
392.2
387.8
389
390.7
383.7
386.1
392.3
386.3

Average 389.91 - 4.9 Ft/Lb