| Term | Definition | Category |
| Gauge | A system of measurement for the internal bore diameter of a smooth-bore firearm based on the diameter of each of that number of spherical lead balls whose total weight equals one pound. | |
| Grains | A unit of weight (mass actually) used for measuring bullets and gunpowder. | |
| Grip | The portion of the stock or pistol where you grasp the gun with your dominate or trigger hand. | |
| Grooves | The cuts made in the bore of a firearm to produce rifling. | |