FPS is velocity; Joules are energy
FPS describes how fast a BB travels. Joules describe the energy carried by that BB and depend on both velocity and mass. The same replica can show a different FPS when tested with a different BB weight.
Chronograph readings are meaningful only when the BB weight, test method and hop setting are understood. Do not compare a number from one site directly with another site's number without checking the method.
The venue rule is the rule
Operators set limits, test procedures, minimum engagement distances and upgrade restrictions for their games. Always check the event page and ask the operator before changing a replica.
Never use this guide to justify exceeding a site limit. If a chrono result is unexpected, stop using the replica and ask the marshal or a qualified Gun Tech for help.
Common questions
Is a higher FPS always better?
No. Accuracy, consistency, hop performance, reliability and the site's rules matter more than chasing a higher number.
Why can FPS change with BB weight?
FPS measures velocity, while Joules measure energy. Changing BB mass changes the relationship between those measurements, so sites should test consistently.