Mind you, all the info were right in the Config folder in the game dir staring at my face. This will ONLY work when the server has enabled MP cheats by setting variable bMPCheatsEnabled to true. After you join a cheat enabled server, pull down the console and type:
mpcheat changeclass ?
where ? can be one of the following:
R - M16A2 AR - SAW (M249) G - M16A2 with grenade launcher S - M81 AK - AK47 S24 - M24 F - Fists! (I kid you not.) M4A1 - M4A1 AK74SU - AK74SU GP - AK47 with grenade launcher? RPK - the opfor machine gun SVD - Dragonov sniper rifle
Use your AltFire key to recharge the sniper rifles. Haven't figured out how to zoom within scope view yet. Server admins should use this with care, since mpcheats also enables some other UT cheats. I recommend this only for practicing with your clan or something. This also works on Rifle Range, but will prevent qualification.