I think we have found a rules difference between the LBBs and the Traveller Book. I couldn't find concealment in either edition of the LBBs.
For addition to your rule set, here are some sections contained in the Traveller Book (word for word)...
Zero Gravity: Virtually all weapons have recoil (except laser carbines and laser rifles) and in a zero-G environment this recoil can disorient or render helpless individuals not trained to compensate for it. When fighting in a zero-G environment, any individual has a chance of loosing control of his or her movement/position each combat round. Throw 10+ to avoid loosing control. DMs: -4 if firing a weapon. +5 if using a handhold. -6 if performing a swing or blow. +2 if DEX 9+. Additional +2 if DEX 11+. Using a handhold reduces DEX (for the above DMs and for required or advantageous dexterity) by -4.
Individuals who lose control may not fire until they have reoriented themselves and regained control. Roll 10+ in each subsequent combat round; DMs as above except handholds and weapons may not be used.
Reloading: Technically, guns reload themselves after each shot. However, when the magazine capacity of a gun is exhausted, then the shooter must reload the gun with a fully loaded magazine. Unless otherwise stated, the process of reloading a gun with a full magazine takes one combat round, during which time the shooter is treated as evading.
Revolvers do not use magazines, and so take two combat rounds (one combat round if not simultaneously evading) to reload. Laser carbines and laser rifles do not use cartridges; their power packs must be recharged upong being exhausted. Such a laser weapon may be returned to service by replacing the power pack. Recharging a spent power pack requires approximately an hour at a power source.
Empty magazines are, of course, resusable. Ammunition for such magazines can be purchased for approximately half the price of a full magazine. the tedium of reloading empty magazines requires that it be done at leisure, rather than combat. The process takes several minutes for each magazine.
Laser rifles and laser carbines require recharging of their power packs at a power source. When cone commercially, there is a cost of Cr200 to Cr300 for the service. Generally, such power packs can be recharged at a ship's power plant at no cost.
Armor: With the exception of reflec, no armor may be worn with another armor. If reflec is worn in conjunction with antoher armor type and the wearer is attacked, the better type of armor provides the DM.
Darkness and Night: Poor lighting conditions may restrict the ability of an individual to see and attack. Total darkness restricts engagements to close and short range. Attacks with guns at greater than short range are subject to DM -9. Partial darkness (moonlit night, distant illumination, or other weak light sources) reduces visibility range to medium, and attacks with guns are subject to DM -6.
Electronic Sights eliminate negative DMs due to darkness and poor lighting.
Cover and Concealment: Cover is any solid object between an attacker and defender capable of protecting the defender from a weapon attack. Concealment is any object that prevents viewing or sighting of the defender. Cover may also be concealment; concealment is not necessarily cover.
An individual under cover cannot be attacked; an individual in concealment cannot be attacked unless the attacker has some reason to shoot in the area.
Individuals who attack from cover become visible and may themselves be attacked; because they retain partial cover they are eligible for a defending DM of -4. Individuals who attack from concealment provide reason to believe they are present, and may be attacked; because they repain partially concealed, they are allowed a defending DM of -1.
I think that the Traveller Book's cover rule is poorly conceived.
We might have to agree to disagree on this one, TBeard. I think CT's combat system works fine, including Book 4.
Don't forget what I mention above when I say...
For example. Dukee, with DEX-7 and AutoPistol-1, fires his weapon and hits his target, doing 3D damage.
The first time the target is damaged, we use the first blood rule. Thus, all wound points are taken from a single stat. Our target has physicals of 777. Damage rolled is 3, 2, 1.
That's six points of damage, applied to STR randomly, making our target have physical stats of 177.
Next round, Dukee lands another hit. He roll damage: 5, 2, 3. Now, since the first blood rule has already been used, the defender applies damage as he sees fit just as long as he doesn't break up a die to do so. So, deftly taking the damage to the defender's benefit, the target ends up with stats of 122.
And, at the end of the second round, the defender fires at, hits, and incapacitates Dukee (first blood rule got him).
What really happened?
Was the defender actually shot twice?
See...when evaluating CT combat, I believe you tend to equate a successful to-hit roll to also mean that the target was shot. As I've shown in this example, that's not always the case. It can't be. Here, the target suffered two successful hits and a total of 6D damage, yet, the target was not incapacitated. In fact, with medical attention, the target is good as new in half an hour (fully healed).
Plus, all stats are considered at their full rating until after combat is complete. So, the only time the target in the above example would have his weight allowance adjusted for the wound would be the 30 minutes he spent with the doc. If the target had a DEX bonus for his weapon, and his DEX was reduced during combat, it wouldn't affect the character until after combat was over.
CT's combat system definitely has an abstract quality to it. It's really up to the GM to declare what happens during a combat round, and I think the best way to ref that is to look at the effects of combat, using that to guide the GM's decision.