I don have a crony, extracting audio with audacity (better than airgun phone app), bands are 20mm x 15mm taper, TBS clone, ammo 7/16" steel
butterfly delay 0.155 secs yields 80 m/s average
full butterfly delay 0.141 secs yields 90 m/s average
velocity near the forks should be higher.
a net 12.5% increase and 26.5% more energy at 10 mts