Here's the rules for your case, since I can not find the link any longer after the forum upgrades.
Any gun wishing to shoot a 0.2gram BB faster than 400fps but less than 500fps must meet these requirements for a sniper rifle classification. The rifle must either be bolt action or semi auto only, the gun must not have the ability to shoot full auto. The second requirement is where the said person using the rifle must obey a 50ft no kill zone with the rifle. Meaning, if someone is within 50ft of you, you cannot fire on that person with your sniper rifle. If you have a secondary weapon that shoots less than 400fps with a 0.2gram bb then you may engage your target with your secondary within the 50ft area but if you do not have a secondary meeting these requirements you will have to surrender yourself as a safety precaution.
Be sure to remember when using the chrono that using a heavier bb to slow down your fps does not meet the requirements of the rules. It must be a .2gram bb for FPS testing purposes.