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Old 06-05-2021, 06:25 AM   #1
MrFix's Avatar
Join Date: Aug 2019
Default Indirect Fire: Understanding rules right?

Trying to truly comprehend how Indirect Fire works. HT139

Predicted Indirect Fire
- Using standard ranged rules.
- Targets are located using a physical map or stand-in item (computer etc).
- Only targets that appear on the map are targettable. Buildings. Forests. Lakes.
- Recon elements can create custom maps that outline temporary objects like tent camps, vehicle parks etc and pass the map to artillery, making them targettable.
- Any hex of an identified target can be attacked.
- Can only attack hex, receive +4 to do so as per Area Attack rules.
- Ranged penalties are in play
- Speed is not in play, target is an immobile hex
- Size Modifier is not in play, target is a fixed-size hex (SM+4).
- ??? Darkness penalties over target do not count since you don't observe the target
- ??? Can aim since you know where you're shooting
- ??? Can't receive fire corrections from the ground beyond fire suggestions: "Stop firing at Building A and fire at Building C to the east, across the road".

Example: Map designates a 10x10 building 1000 (-16) yards away. Artillery chooses to attack it's dead-center hex. It's night, but artillery installation has ample lighting to operate the gun (+0 darkness penalties). Artillery has Acc 3 and is attacking a hex for +4. Artillery crew base skill is 14.

14(Skill)-16(range)+3(acc)+4(hex)=5 effective skill.
Crew rolls 10, failing their roll by 5. This scatters the shot by 5^2 yards, or 25 yards. They roll 1d6 for scatter and get 6. The shell overshoots the target and lands 15 yards away from the target's edge. The artillery crew does not know the effect of their attack.

Observed Indirect Fire
- Standard Ranged Attack rules do not apply. Forward Observer rules REPLACE them.
- No need to define location or distance from Artillery unit to target beyond in-range/out-of-range.
- No penalties matter to the artillery installation, only blanket -10, regardless of their equipment. Artillery Accuracy does not apply. Bonus for attacking a hex does not apply.
- Forward Observer needs to designate target. He uses Aim/Concentrate maneuver to designate it, spending 2d6+5 seconds to do so.
- He makes Forward Observer roll, modified by All Vision Modifiers: speed, size, lighting, his forward observer equipment. Specilized Range rules are used to replace normal range table.
- The target can be a hex, or specific unit. Forward Observer gets hex's +4 to his Forward Observer roll. Can target anything including single infantryman.
- Forward Observer makes Forward Observer roll. Margin of Success/Failure is added to Artillery's blanket -10 penalty.
- ??? It is possible that penalty may exceed -10, to -11 etc if FO fails his roll enough times/for enough margin.

Example: Observer designates a 10x10 (SM+6) building. Observer is 500 yards away from the target (-3 special range penalty). He's equipped with digital TL8 laser target designator (+3). The target is not using stealth or camouflage, and is in plain sight (+10). It's bright day, so he has no penalty from darkness (+0).

He spends 2d6+5 seconds performing designation. FO Skill 14.
14+6-3+3+10+0=Effective Skill 30. He rolls a 10 and thus his margin is 20.

Artillery prepares to fire, their penalty is blanket -10+FO's success margin, but no more than +0. Artillery crew skill is 14. The margin of FO completely eliminates blanket -10 penalty.

Artillery fires and rolls 10. 14-10=4 margin of success. The artillery strikes target with direct impact.

Did I get that all right? I'd like to hear comments, especially on the lines marked with ???.
Your level of GURPS proficiency:
Pedestrian: 3e vs 4e
Proficient: Early 4e vs Late 4e
Master: Kromm vs PK

GURPS: Shooting things for fun and profit

Last edited by MrFix; 06-05-2021 at 06:36 AM.
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Old 06-26-2021, 10:58 AM   #2
MrFix's Avatar
Join Date: Aug 2019
Default Re: Indirect Fire: Understanding rules right?

Just came to realization that since Forward Observer is a skill, and that +10 for in plain sight only applies to pure vision roll, it doesn't apply to Forward Observer rolls.
Your level of GURPS proficiency:
Pedestrian: 3e vs 4e
Proficient: Early 4e vs Late 4e
Master: Kromm vs PK

GURPS: Shooting things for fun and profit
MrFix is offline   Reply With Quote

artillery, high tech, high-tech, mortar

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