Corporal Jones moment coming on here....
When I was running the Wargames Centre in Ayrshire ( now biohazard), as a CQB style indoor site we had a limit of 328fps (+/- 10) and always tested on .2s. As it got busier we had more issues just chopping and changing mags etc to chrono.
We had guys turning up when hpa was becoming more common and we had issues with understanding locking settings etc. The same with guys having MK23s with the suppressor which took pistols over 380-400 fps.
Theres also different gases that can ramp fps.
As said before, if someone has a hard-on so bad to chrono at the site limit then quick change/regas/use magic then they are going to do so.
I've had people who chrono over the fps saying they'll use heavier beebs, which doesn't help, as the energy is still there.
We did give someone a ban for using a hot gun, and I definitely kicked players off site for aggressive behaviour.
The trouble with infractions, some of them genuine mistakes, is that at the end of the day, everyone wants to play safely and honestly, there's always going to be a dick in there, and there's a fine line between punting players/getting a name for being an overly strict site and paying the rent and rates.
As much as I/we voice support by playing honestly and by the rules, you get a different experience when you're having to use your own money to tide over the site as you build your legit player base. ( and that is just my experience, I am not in favour of anyone cheating/bending the rules)