beam weapons behave a lot more like lasers than the actual lasers do in FS. lasers are EM waves, meaning they would travel at the speed of light, not ~400 m/s bolts.
but i'm going to revert back to my favorite argument, that this is a game and not a class in physics, so it doesn't really matter. to me at least.
I'm Thaeris and I endorse this message.
Beams are not more likely to be lasers than any other 'realistic' explanation of what they are.
Lasers could, hypothetically, use a plasma core as part of the lasing medium. So that fits. They also travel instantaneously at these ranges, just like beams. Those are the big points in favor of the 'laser' theory.
However, lasers do not sidescatter like beams do. Lasers do not charge up with bright glowing particles around the emitter. Lasers do not travel a fixed distance at maximum power and then stop working. :V: called everything which was a laser - no matter how bizarre and aphysical -
a laser, but did not do so for beams.
And, most importantly, in FreeSpace? Shields block lasers. (See above for why yes, that includes visible light.)
So it ends up being just as much of a kludge as any other explanation. It's not necessarily a bad one but it's not a good one either.
In the end, beams are beams, and you're just going to drive yourself nuts trying to make them make physical sense.