I used the following gear: Sylvan gapette +2 (+5%), unaugmented Iuitl Wristbands +1 (5%), Sylvan Caban +2 (allegedly makes Velocity Shot a 20% reduction), Lutian Cape (+3% augmented), Impulse Belt (3%), and Taeon Boots (+5% augmented). I used Relic Gun (w/ Bronze Bullets) since its high delay makes it easy to compare delay reduction results. I also have max Snapshot merits. I figured with merits, gear, enhanced Velocity Shot, and Flurry II, I could reach 80% Snapshot and I could compare measured delay at 71% Snapshot.
I equipped one piece at a time to confirm their listed values (factoring in my merits) and they all fell within a reasonable range of (999/120) * (1 - Snapshot) + .4 seconds. I did this all without Velocity Shot (excluding Sylvan Caban). I also used trust Koru-Moru and confirmed a value of 30% Snapshot from Flurry II. So I proceeded to combine all of these pieces.
The theory wasn't matching up with the experiment. I tried isolating what was causing the error and could only really come up with the Sylvan Caban. With head/hands/feet/waist/back/merits, I have a combined total of 31%, so a theoretical delay of (999/120) * (1 - .31) = 5.744 sec. I had an actual average delay of 6.148 sec (discarding obvious rapid shot data), and 6.148 - .4 = 5.748 which is pretty much exactly what you would expect. I added Flurry II (total 61% snapshot), and I had a maximum of 3.431 sec which falls within reason.
However, when I add Sylvan Caban +2 and pop Velocity Shot on top of that, I recorded a maximum value of about 2.977 (I only did about 30 shots but most of them were around ~3 seconds). At 80% reduction, you would expect the delay to be about 1.665 sec, which clearly was not even close. I thought maybe the recorded value of the Sylvan Caban was wrong, but with just Caban, V Shot, and merits I got an average of about 5.825 sec, which isn't too unreasonable for a 20% reduction factoring in a .4 sec error.