Well, I have studied beam weapons, you CAN have some, though no real ones, but it depends on how you make it. There are two versions of beams:
First of all, the "Fragment Beam": Most realistic because of extremely high refire; It should consist of short beam "fragments".
Then comes the "Sniper Beam": it's called so because you have to hit a single time, with the tip. The beam should be long so it looks like a beam, but it doesn't handle like one.
So here's my suggestion: A mix of both versions, refire like the new Chain Guns, and beam "fragments" so long that the projectiles "merge" into one beam.