GURPS TL4 Gun Stats

Computed GURPS Stats

Weapon Input

Auto-derive dependent inputs with historical estimator

When this is on, changes to the weapon inputs feed the historical estimator and update the dependent weapon inputs it can derive, mainly projectile weight, charge weight, and muzzle velocity.

Weapon name Date Configuration Historical velocity family Pistol grip Stock Bipod Action Gun lock Barrel type Caliber (inches) Barrel length (inches) Overall length (inches) Empty weight (lb) Projectile weight (grains) Muzzle velocity (fps) Length-to-diameter ratio Charge weight (grains) Actual projectile diameter (optional, inches) Patch thickness (optional, inches) Shot weight for artillery (optional, pounds) Charge override (optional, grains) Powder REF Baseline REF Lambda override (optional) Ignition / condition factor Projectile class Cost ($)

TL4 assumptions in this app

TL4 is treated as 1450-1729.
The calculator is intentionally scoped to TL4 firearm patterns.
Projectile class support is centered on solid shot; shot uses simplified recoil handling.
Automatic actions, magazines, metallic cartridges, and TL5+ options are omitted.
You can still enter a caplock or breechloader if you want a border-case prototype.

Quick conversions

1 mm = 0.039 in
1 m/s = 3.28 fps
1 lb = 7,000 grains
Gauge to caliber: cube root of (1.05 / gauge) x 1.643
Pounder to caliber: cube root of pounder x 1.97

Research Conversions

Use this to turn research figures into ready-to-go inputs for the calculator. In these rules, bore is synonymous with caliber.

Caliber to Inches

Caliber in inches Millimeters Centimeters Shotgun gauge Pounder

Velocity and Weight Helpers

Meters per second Grains Pounds

Ammunition Cost Helper

Powder charge (grains) Projectile weight (grains) Projectile material

Historical Velocity Estimator

This helper uses the family-based black-powder model to estimate projectile mass, charge, fit, seal, and muzzle velocity from sparse research data. It is intended for round-ball firearms and round-shot artillery only.

Estimator Inputs

Weapon family Bore / caliber (inches) Barrel length (inches) Actual projectile diameter (optional, inches) Patch thickness (optional, inches) Shot weight for artillery (optional, pounds) Charge override (optional, grains) Powder REF Baseline REF Lambda override (optional) Ignition / condition factor

Minimum core inputs: weapon family, bore or caliber in inches, barrel length in inches, and powder REF.

Strongly recommended overrides: actual projectile diameter, patch thickness for rifles, and shot weight for artillery.

TL4 firearm builder