Weapon Ranges

Grizbe is right. Laser beams diffract (spread out, to you).

A handy little equation for calculation the diffraction of a laser beam at a given range is:
RT = 0.61*D*L/RL
where:
RT = the radius of the beam at the specified range in meters
D = The range from the focusing lens or mirror in meters.
L = The wavelength of the laser light in meters
RL = The radius of the focusing lens or mirror in meters.

Depending on the raw power available, the wavelength of your laser and the size of your lens there is a very finite upper limit to the effective range of a laser weapon.

However - instinct tells me that the range listed in the book for a given weapon is simply 'effective range' - which is another animal entirely and takes into account things like accuracy and projectile speed.

Lasers have constant speed (subject to medium, of course), bullets start very fast and slow constantly over time. Bolts start slower, then accelerate, then slow again.

Actually - Meltas are:

1) Microwave emitters - this is old fluff - but I sort of like it. It's cool and different and explains their rules quite well.

2) Meltas work via subatomic agitation of hydrogen. Let's face it, GW isn't exactly staffed by physicists, but if I had to guess I'd say they're some kind of hydrogen-maser. Still, therefore, microwave based, but not very realistic given the known properties of hydrogen masers.


Imperial plasma weapons are a different kettle of fish. My own theory is somewhat offbeat. If you've ever seen a Tesla coil in action you've seen the ribbons of plasma discharged by it. aiming is a problem.

A high-energy laser beam would ionize the air for a fraction of a second and if in that time, a tesla coil were discharged the plasma would follow the highly conductive ionized air - which being caused by a laser, is dead straight.

Look at a 40k plasma weapon - you'll see a part that looks like it might be a coil. This also explains why the sometimes hurt the user - any flaw or problem with the laser beam - including mere atmospherics, would leave the plasma streamer nowhere to go - so it'll take the easiest path to ground - straight through you!