As noted above, after discussion here and on the ADB board, we've modified the rules for the Seltorian (Tholian) Particle Cannon. The to-hit/damage chart remains the same. The cost of standard and OL remain the same. The modifications are that the 12-impulse delay is lowered to the normal 8-impulse delay and the PC may do a 'combined shot' which simply combines the OL and standard shot (only shot of the turn) at a cost of 5 + 1 from battery at the time of firing. 32-impulse cool down delay.
I'm looking at changing this somewhat based upon characteristics of the PB.
The Particle Beam is a one-turn weapon like the PC. It has an 8-impulse delay and can fire up to twice per turn. One point allows for a standard shot. Two points allows for either two standard shots or one OL shot. Three points allows for one of each and four points allow two OL shots. The range breaks are similar but the PB is a bit better overall though the damage done is slightly less. Both have a 0 range break. The PC has a 1 whereas the PB is 1-2 (both for a 1-5 to-hit). The PC has a 2 and 3-4 (1-4 to-hit) whereas the PB has a 3-4 and 5-6 for the same 1-4 to-hit. PC has 5-8 and 9-15 for 1-3 to-hit while the PB has 7-8, 9-15 and 16-24 for the same 1-3 to-hit. As noted the PB is slightly less damage. Overall the PB is a superior weapon to the PC.
I'm thinking that a 32-impulse delay for the PC cool down is unnecessary. I'm also thinking that the 1 point from the battery at the time of firing is unnecessary. With this line of thinking, at R8 the PC with a combined shot would do 9 points of damage in one turn at a cost of 5 points of power, whereas the PB, if able to get in both OL shots can do 8 points of damage for 4 points of power. At best, the PC will do 12 points and the PB will also do 12 points (if both OL shots get in).
That would put the PC a bit more in line with the PB but still be somewhat unique from each other. That's my conclusion at the moment while I evaluate both weapon systems.
Courtesy of Peter Bakija:
"So in messing around with the Vari:
-Particle Beams: These are not actually that horrible, given that they can fire twice per turn/once every 8 impulses (which is significantly better than the Particle Canons). They are actually more energy efficient than Disruptors most of the time:
Range 0: 3 damage/energy (disr do 2.5)
Range 1-2: 2.5 dmg/energy (disr do 2)
Range 3-4: 2 dmg/energy (disr do 1.3)
Range 5-6: 1.3 dmg/energy (disr do 1)
Range 7-15: 1 dmg/energy (disr are 1)
But they lack crunch power (at R1, an OL is hitting for 6 damage, where a disruptor is doing 10 for twice the power). If you can fire them a lot, it adds up, and Particle Beams will eventually come out ahead of disruptors. But that is hard to do, as you can't hold them, so you have to spend a lot of energy arming them every turn (but then, Disruptors have the same problem. But also are harder hitting in any given shot). In a close knife fight, PBs actually can be pretty good.
I think if you could hold them (pay 1/2 the power in the gun to hold; so if you put 4 in to the PB on turn N and don't fire it, you can hold that power for 2 on the next turn), they'd actually be pretty good.
-Particle Probes: These are clever little guns (they allow you to basically do 3 damage through any down shield as long as your opponent is within 6 hexes) with all sorts of problems. They are relatively expensive to arm (1+2 power for a single Particle Beam) and you can't hold them. You can only launch 1 per turn ever, even with multiple PP launchers. On the upside, you can always just fire one to get an extra PB in your volley. On the down side, putting 3 power into 2 of these per turn (one with 1 power to fire next turn, one with 2 to fire now) is really unlikely. Best case scenario, you have one armed for 2 power the turn your are engaging and can get a small, auto second mizia volley.
Much like the Particle Beams, if you could hold them (1 power, say), they wouldn't be that bad.
-Particle Phasers: Very random, but with some lucky dice in close, they can do a lot of damage. In close, they are a little better, on average, than P1s. Out past, like, R3, they are a little worse. But if you get a couple 1's or 2's in any volley, you can do a lot of damage."
With all that in mind, they are generally comparable with the Selts PC. Though as you point out they lack in one-shot crunch power. This is where the PC combined shot can start to make more of a difference. With the PC combined shot you can get from 9-12 points of damage in one-shot. That isn't terrible at all and comparable with the Disruptor or Ion Cannon (but with worse range breaks).