This is what I currently use:
Expanded and modified High Guard/LBB2 rules to allow for small ship (5000 tons or less) combat.
Weapon Rules
Missiles – Per LBB2 missiles will always hit the target unless stopped by countermeasures. Missiles are fired at end of turn, and hit at end of following turn.
• ECM program stops all incoming missiles currently in flight on a roll of 7+
• Anti-Missile: Lasers can destroy one incoming missile on a roll of 8+ (+1/2 Gunnery skill, and +1 per laser in turret above the first one). Lasers used to fire on enemy targets are allowed to fire on incoming missiles.
• Sandcasters: Each incoming missile must save at 11- on 2D6 if sand is fired
Missile Types – Missiles may be fired from turrets or bays. Bay missiles (commonly called torpedoes) cannot be fired from turrets, but can be launched from ordnance hardpoints on small craft so equipped. A 50-ton missile bay fires 2 torpedoes at a time, a 100-ton bay fires 4.
• Standard HE: does 1D6 hits (less armor) applied randomly
• Standard HEAP: does 3 points damage (less armor) to one location
• HE Torpedo: as standard HE, but 3D6 hits
• HEAP Torpedo: 8 points damage (less armor) to one location
Energy Weapons – Each turret rolls only once to hit a target. All fired energy weapons in the turret hit on that single roll. For example, a triple laser turret firing all its weapons rolls once to hit, and then once on the location table for 3 points of damage against that location less armor.
• Beam Lasers – Beam lasers hit at 8+ (+/- appropriate DM) and do 1 point of damage each.
• Pulse Lasers – Pulse lasers hit at 10+ (+/- appropriate DM) and do 2 points damage each.
• Plasma / Fusion Guns – Both are short range weapons that can be fired from turrets and bays. Plasma guns do 3 points each, Fusion guns do 4. Bay versions are increased by 2 points.
• Particle Accelerator Weapons (PAW)-
• PAW turrets do 3 points damage (less armor) plus both crew and computer must save 9+ to avoid radiation damage. If failed the computer takes 1 point damage, crew take 1D6.
• PAW barbettes do 4 points (less armor) and 2 points/2D6 radiation damage
• PAW Bays 50-ton bays do 6 points damage (less armor) plus 4 points / 3D6 radiation damage. 100-ton bays do 10 points damage (less armor) plus 6 points/4D6 radiation damage.
Personal armor reduces radiation by that armor’s point value.
Sandcasters – Sand will stop incoming laser fire at a rate of 1 canister of sand per laser stopped. For example: a triple laser turret would do 3 points damage if it hit, but only 1 point if 2 canisters of sand had been fired.
• Sand is launched at the end of the turn and counts towards the next round of laser fire.
• Sand only lasts one round of laser fire.
• Launchers may only launch one canister per turn.
• Sand will not stop fusion/plasma guns or PAW fire.
Armor – Ships may be armored per High Guard rules.
Boarding Actions
In all matters concerning maneuver the ship with the highest agility rating will dictate the range between ships.
To board another ship, its vector and velocity must be matched. To force a boarding the attacking vessel must have a higher agility than the target. If this is the case then the pilot of the boarding vessel must roll 10+ (plus Pilot or Small Craft skill as DM) to match course and lock the craft together.
The high roll is to simulate any desperate maneuvering the target ship may try at the last minute.
Damage Control
Critical hits may not be repaired since the damage has destroyed the component.
Components damaged to zero cannot be temporarily repaired more than to half their original value. For example: a Jump-2 drive damaged to 0 and then repaired will only function as Jump-1 until permanent repairs can be made.
Turrets hit twice are destroyed and may not be repaired,
All repairs are considered temporary only and will fail after the next jump unless more permanent repairs can be made in a shipyard.
The time required to make a repair is equal to 2D6 combat man-turns minus appropriate skill level. For example: the Jump Drive takes two points damage in combat. The Engineer rolls 2D6 and gets 5…less Engineer-3 equals 2 combat man-turns to patch things up. It means the Engineer will need 2 turns working by himself, or only 1 if another character with Engineer skill helps.
...Sorry for the length. Some of the damage,like for PAWs may not seem enough, but it's more than sufficient when you consider that IMTU most civilian vessels are not armored or armed. Fusion/Plasma guns are the carronades in space, carried by the 1000 ton destroyers for close-in "clearing the decks" before boarding. Lasers are mainly for anti-missile/small craft defense. I also view PAW barbettes vs. turrets in a more traditional configuration: barbette being a heavier gun than what you'd fit in a turret. So I reversed what is in High Guard, besides, IMTU the average TL is only 13 so the turreted PAWs are not found.