I speak only from my own experiences.You can use them as primaries,but you have to keep some things in mind.Using one in games will definitely change how you play in comparison to an electric.The biggest change will be getting used to using semi quite nearly exclusively.Not just because of the ammo count per mag,but to manage your mags period,and gbb's are the absolute most accurate in semi.When out in the field with one your mags will be a priority.In order to keep the weapons consistency the same every time you do a reload your going to want to give your mags a 3 sec or so shot of gas.I carry a Coleman propane tank with me in a magazine dump pouch on the very back of my hip.You will absolutely find yourself being more selective with your targets,and only selecting those you believe you have the greatest chance to hit.To achieve this your going to find yourself engaging targets using stealth,(from concealment,stalking, etc),setting up ambushes,and that kind of thing.Because of this,your gear will change.I've found selecting camo that actually works,and combining it with other forms of camo to break up your silhouette works best.Traveling light works best as your going to find yourself doing alot more moving around from cover to cover in order to setup shots,and to keep enemy players guessing at your location.I have found it best to stay clear of friendly players who use electrics,and groups of players also.Allow players with electrics to initiate a fire fight first while you outflank enemy players to setup shots,and pick them off.Your going to find the aeg players make alot of noise,and in general draw alot of attention to themselves which is everything you don't want.Teaming up with snipers is alot of fun as both are more like minded,easier to setup flanking maneuvers, and shots (atleast two of you working together).For gbb's range and accurate semi fire is everything.I make all of mine as mechanically efficient as possible.ALL moving parts are polished,liberally lubricated,and I tune all mine for the longest,straightest,ammo flight I can possibly get them to,and heaviest ammo my guns can lift while remaining within the rules where I play.The more efficiently and smoothly they run the quicker your follow-up shots are,the more consistent they are,and they are less likely to succumb to a failure.Heavier ammo is crucial for the best range and accuracy you can manage.In short, your going to find yourself adopting more of a sniper/dmr style of play than what the electric guys do.