Here's the rules for fps. from their website. They don't chrono guns before the game, and players 15 and up are NOT required to wear full face mask.
b) Gas weapons
(1) Gas pistols are recommended for use in any game. The requirements on these guns are: They must be firing under 450fps for outdoor games, 350fps for CQB; They shoot a plastic 6mm or 8mm bb; They use Green gas, Propane, Duster, HFC134a, Red Gas, Blue Gas, G17, C02, ect.. Under no circumstance will Nitrogen or Nitrous be allowed on any field of an MMA game.
(2) Gas sniper rilfes are recommended for those taking on the sniper role. Use the same requirements as 301(b)(1) and limit to 550fps. A minimum 50ft distance for rifle use will be enforced. If a sniper is within 50ft from the player, s/he must use a pistol.
(c) AEGs
(1) AEG (Airsoft Electric Guns aka Automatic Electric Guns) are the most recommended for game play. They must shoot only 6mm plastic bb's and shoot under 415fps (with .2g bb's) for outdoor games, under 350fps (with .2g bb's) for CQB games. There is no minimum or maximum magazine capacity or any upgrade rules other than the Feet per second limit.