in weapon_equip.ini you will find a line on the guns that says refire_delay = XX.XX
To get this you use the equation

1(this is time in seconds and is always 1), divided by the refire rate, equals the refire delay. Than place the refire delay in place of the existing number. Or create a completely new weapon.

So the equation is 1/RR=RD

I got this info from the various tutorials on LancersReactor so thank the tutorial writers, not me.

Look in the tutorials section

There are 2 mods that come with FLMM that create a Beam wepon, that is fast refire rate. Check it out and see.

I have seen and tried weapons with refire rates as high as 100per/sec. As a practical matter though, refire rates higher than about 32/sec are really not more effective, and the best weapons I've made seem to be with refire rates of 8-16/sec. Why..? I think the game cannot add up the damage fast enough with the highest refire rates so that many hits just do not count. The same seems to apply to very high damage rates. I have experimented with guns with hull and shield damage rates as high as 18000 but if you experiment with them at a refire rate of 2/sec or 8/sec it sometimes takes just as long to kill a Titan, for instance, with the more powerful gun as it does a lesser one. All told, the most effective guns seem to top out with damage rates per/sec of about 10,000 to 15,000, though I'm sure there are exceptions. With the higher damage guns you will also find that more than 4 don't really get you much either, as you can sometimes kill 'em quicker with less than more. Also, you will occasionally encounter an NPC that no amount of shooting will destroy in a continual barrage. It seems like you have to break off and come back for another pass in order to destroy him no matter how well you hit him the first time. Perhaps as the new computer systems with the faster PCI Express busses with 2 video cards and full-on 64 bit processors and operating systems come online these restrictions will vanish... but I doubt it.

There are several tutorials available in the tutorials secton concerning modding weapons... one even by, well... me!