Fundamental: Ranged Combat

First interesting image result for
"Ranged Weapons." The rules for
guns, bows, thrown weapons, and many
missile spells are similar in GURPS.

I was asked to write a bit of a guide on how ranged combat works. I don't think it's especially difficult to understand versus melee combat, so I'll focus on the "gotchas" and the parts I get wrong the most. Without further ado, let's get the ball rolling.



First off, to get some grasp of ranged weapon combat, I recommend reading this simple but verbose example of two people standing out in the open and shooting at each other. Read the other 3 examples of ranged combat while you are at it (this one is "example 3," but it feels like the most "typical" and "vanilla" of the examples.) With most of what actually matters explained in detail, I'll break it down further in a more generic way, component by component.
For the sake of this post, let's use the attributes of one gun from the Lite version of GURPS.

TL	Weapon	Damage	Acc	Range	Weight	RoF	Shots	ST	Cost
6	Auto Pistol, 9mm	2d+2 pi	2	150/1,850	2.4/0.4	3	8+1(3)	9	$350

Loading Weapons

Each ranged weapon has a shots attribute which indicates how many bullets/arrows/charges/what have you can be loaded at once. If more than one is loaded at a time, you don't need to reload more than once. Though there are a few nuances, I'll focus on the two most important pieces of information this stat communicates:

• The amount of ammunition that can be loaded at once. This is the first number in the shots statistic. If you notice, the example has "8+1" which means a full load is 8 bullets, but in addition, one can be in the chamber.
• The parenthetical number is the seconds it takes to reload the gun. If the number is followed by an "i" that is the time it takes to reload each round, which makes sense for some guns, like double barreled shotguns or revolvers, where you might only care about loading one or as many shots as you can get while behind cover in the middle of a battle, and you don't have the time to load the entire thing.

If you have the Fast-Draw skill for the type of ammunition your weapon has, you can reload one turn faster. So, for this example, someone without Fast-Draw would take three seconds to load the gun, but with Fast-Draw, it only takes two seconds.

Aiming Weapons

Ranged weapons are subject to range penalties that make what might be decent skill levels for a melee weapon, barely tolerable to unacceptable for a ranged weapon. Thus, aiming is often critical. The Acc stat tells what bonus one can get for aiming for one turn. In addition, it is the norm that a player may aim for two additional turns to get a bonus of 1 for each of those turns. In this example, if we aim for one second, since we have 2 Acc we get a bonus of 2 to our skill, if we aim for 2 seconds, we get a bonus of 3, and if we aim for the full three seconds we get a bonus of 4.

Rate of Fire and Recoil

Interestingly, the Lite stats don't include a Rcl, or Recoil stat for this gun, but going with a typical recoil value, let's pretend it is 2. We do have an RoF, or Rate of Fire stat though. These two stats indicate the gun can consume more than one bullet a turn, and that they may be able to wound a target multiple times. Our Auto Pistol has an RoF of 3. We can fire 3 shots in a second. Rcl tells us how hard it is to hit with more than one shot. If we pretend that Rcl is 2, that means each additional hit requires an additional margin of success of 2. So, pretending we have an effective Guns (Pistol) skill of 15 after accounting for Acc and range penalties, then:

• If we roll more than 15, we definitely miss, just like any other weapon.
• If we roll 14 to 15, we hit with one bullet (1 + MoS/2, 2 being the Rcl on the gun, rounds down to a minimum of 1)
• If we roll 12 or 13, we hit with two bullets (1 + MoS/2 rounds down to 2)  
• If we roll a 11 or less, we hit with three bullets (1 + MoS/2 rounds down to a maximum of 3, our RoF) 

Most weapons allow the user to fire less than the maximum RoF, maybe for the purpose of saving bullets, or to maim but not kill a target. High RoF values give a bonus to skill, but only if using enough bullets to count.

For Active Defenses against several bullets that hit (eg, if we rolled an 11 or less, and had 3 potential hits) One must succeed at their defenses by 1 to defend against each hit, that is, to say the target has a dodge of 12:

• If the target rolls more than 12, all three shots hit.
• If the target rolls 12, one shot is dodged
• If the target rolls 11, two shots are dodged
• If the target rolls 10 or less, all shots are dodged.

Range

Range on ranged weapons is communicated as two numbers. This is called "1/2D." The first number in the "fraction" represents how far you can shoot and still do full damage, the other number is how far you can hit a target at all. If a target is beyond the first number, but no further than the second number, you may still hit, but damage is divided by 2.

Shotguns

Shotguns have slightly complicated mechanics, and a different RoF stat than most other weapons that is represented as a number in the format "MxN." M is how many shots can be released in a second, and N is how many projectiles exist for each shot. The damage of each projectile is usually a lot less than any one bullet from a pistol or rifle, but at a common RoF of 3x9, which usually means around 27, each projectile doesn't need to be that strong to seriously injure a target. More details can be found on p.409 of Basic Set - Campaigns.

Malfunctions

Malfunctions are an optional rule that can add realistic complexity to guns, and rules for such can be found on p.407 of Basic Set - Campaigns. Typically, the Malf stat is determined by the Tech Level, or TL of the gun, but some guns are slightly more or less prone than average to malfunction.

Firearm Accessories

Basic Set - Campaigns, p.412 lists some interesting accessories that can help with guns, most especially interesting are stands which allow a gun to be considered braced, and Scopes, both of which can help with aiming a gun, in exchange for decreased maneuverability or requiring extra time.

Other Thoughts

Most of these rules, again, easily apply to other ranged weapons besides guns. For other blogs that focus more on guns and probably have more useful detailed information, I recommend looking at:

• Gaming Ballistic As the name implies, the author knows things about guns and GURPS
• Shooting Dice This blog breaks down scenes from movies into GURPS mechanics, explaining, for example, what maneuvers are being used, what techniques and skills are being used, how or why something works, etc.