Not sure how the rules are where you play, but where I play the guns are chronoed using .20 gram bb's.
If you have lighter bb's try using them when you chrono, however with the amount of play you have between the cylinder and piston you could also have an airleak. Try fixing that either with tefflon tape or new o-rings then re-chrono using a lighter gram bb.
If you have lighter bb's try using them when you chrono, however with the amount of play you have between the cylinder and piston you could also have an airleak. Try fixing that either with tefflon tape or new o-rings then re-chrono using a lighter gram bb.