Simply add "$FOF: 0.20" after the last entry for each weapon that you want to affect in the weapon table, without the quotes of course.
It should look something like this:
#Primary Weapons
$Name: @Subach HL-7
+Title: XSTR("GTW Subach HL-7", 3243)
+Description:
XSTR( "Standard Issue
Level 3 Hull Damage
Level 2 Shield Damage", 3244)
$end_multi_text
+Tech Title: XSTR("Subach HL-7", 146)
+Tech Anim: Tech_Subach_HL-7
+Tech Description:
XSTR(
"Descriptive text...", -1)
$end_multi_text
$Model File: none
@Laser Bitmap: newglo9
@Laser Glow: 2_laserglow03
@Laser Color: 250, 0, 0
@Laser Color2: 0, 0, 250
@Laser Length: 10.0
@Laser Head Radius: 0.90
@Laser Tail Radius: 0.90
$Mass: 0.2
$Velocity: 450.0
$Fire Wait: 0.2
$Damage: 15
$Armor Factor: 0.9
$Shield Factor: 0.7
$Subsystem Factor: 0.3
$Lifetime: 2.0
$Energy Consumed: 0.20
$Cargo Size: 0.0
$Homing: NO
$LaunchSnd: 76
$ImpactSnd: 85
$Flags: ( "in tech database"
"player allowed"
"stream")
$Icon: iconSD4
$Anim: SD4
$Impact Explosion: none
$FOF: 0.20
#End
Feel free to play with the value. The 0.20 is just what I've set it at. You can have some fun with ridiculously high settings though. As I said, at 0.20, the shots don't disperse outside of the target reticle, so you aren't going to miss much with this unless you are at extreme ranges. It just looks a little better than the straight line of shots that you get by increasing the rate of fire.
Also, don't get me wrong. I've played through FS2 and 1 numerous times before I even learned how to edit tables, so I simply look at this as a way to breathe new life into an old game. Then again, that's why we are here, right?