Radical Alternatives: How SHOULD Size and Speed/Range Affect Chance to Hit?

Pursuivant · 01-13-2020, 07:09 AM

One big issue that GURPS misses when dealing with Range/Speed calculations is deflection shooting.

It's generally a trivial problem when aiming a relatively close and slow-moving targets, like humans maneuvering in a firefight, but it becomes a real hassle when shooting at more distant and faster-moving vehicular targets.

As an example, it was estimated that aerial gunners during World War II put less than 1% of their bullets on target in combat when shooting at enemy fighters (say SM 3 to 5, traveling at relative speeds of 100 to 1,500 yards/meters per second, at ranges of 100 to 1,000 yards/meters). Just 2% accuracy was expected for graduates of aerial gunnery schools, based on shooting at target drogues pulled by relatively low-speed aircraft flying predictable patterns while firing from a relatively low-speed airplane.

Even shooting at a target coming straight at you (0 degrees deflection) is a potential problem if you don't know the range and there's significant bullet drop.

Arguably, Speed penalties should be increased if taking the shot requires you to quickly traverse your gun while also estimating range and "angle off" on the fly.

Long range shots should be further penalized by speed modifiers if there's any significant projectile travel time unless you have some means to accurately predict range, target motion, flight time, and projectile drop.

Another issue is Inherent Accuracy, especially when dealing with lower TL weapons at longer ranges. For example, a TL5 smoothbore musket is going to have a target grouping which exceeds the area covered by a man-sized target at much more than 50 yards/ meters of range. (One military writer of the time wrote that you had as much chance of hitting the man on the moon with a musket shot as hitting a man standing at 100 paces.)

GURPS 3E made a clumsy attempt to model this by ruling that Acc bonuses didn't apply beyond 1/2D range, but a simpler rule might be to rule that your maximum modified skill with any ranged weapon not specifically designed for accurate long-ranged shooting can't exceed the weapon's TL + 10.

01-13-2020, 07:09 AM	#9
Pursuivant Join Date: Apr 2005	Re: Radical Alternatives: How SHOULD Size and Speed/Range Affect Chance to Hit? One big issue that GURPS misses when dealing with Range/Speed calculations is deflection shooting. It's generally a trivial problem when aiming a relatively close and slow-moving targets, like humans maneuvering in a firefight, but it becomes a real hassle when shooting at more distant and faster-moving vehicular targets. As an example, it was estimated that aerial gunners during World War II put less than 1% of their bullets on target in combat when shooting at enemy fighters (say SM 3 to 5, traveling at relative speeds of 100 to 1,500 yards/meters per second, at ranges of 100 to 1,000 yards/meters). Just 2% accuracy was expected for graduates of aerial gunnery schools, based on shooting at target drogues pulled by relatively low-speed aircraft flying predictable patterns while firing from a relatively low-speed airplane. Even shooting at a target coming straight at you (0 degrees deflection) is a potential problem if you don't know the range and there's significant bullet drop. Arguably, Speed penalties should be increased if taking the shot requires you to quickly traverse your gun while also estimating range and "angle off" on the fly. Long range shots should be further penalized by speed modifiers if there's any significant projectile travel time unless you have some means to accurately predict range, target motion, flight time, and projectile drop. Another issue is Inherent Accuracy, especially when dealing with lower TL weapons at longer ranges. For example, a TL5 smoothbore musket is going to have a target grouping which exceeds the area covered by a man-sized target at much more than 50 yards/ meters of range. (One military writer of the time wrote that you had as much chance of hitting the man on the moon with a musket shot as hitting a man standing at 100 paces.) GURPS 3E made a clumsy attempt to model this by ruling that Acc bonuses didn't apply beyond 1/2D range, but a simpler rule might be to rule that your maximum modified skill with any ranged weapon not specifically designed for accurate long-ranged shooting can't exceed the weapon's TL + 10.