Weapon statistics will look much like this,
Machine Gun: range; 100 meters, damage; 1d6, type; rapid, cost; 300 irinum

The first part is the name of the weapon (self explanitory, if this is just too obivous for you just skip ahead), the second is the range of the weapon. It cannot go past this range and still be expected to hit with any accuracy. To hit roll 1d20 and add your marksman bonus.
Damage is quite obviously, how much it hurts to be hit by it. To damage a creature roll one 1d6 for this particular weapon and it takes that much, simple as that.
The type determines how many attacks you can make with it in a round.

Machine Gun: range; 100 meters, damage; 1d6, type; rapid, cost; 300 irinum

Shotgun: range 50 meters, damage; 3d6, type; medium, cost; 250 irinum

Sniper: range 200 meters, damage; 3d10, type; heavy, cost 450 irinum

Rocket Launcher: range 40 meters, damage; 5d10, type; heavy, cost 500 irinum *

Handgun: range 70 meters, damage; 1d6, type; light, cost 150 irinum

Flamethrower: range 30 meters, damage; 3d12, type; heavy, cost 500 irinum **

Grendade: range 20 meters, damage; 4d12, type; heavy, cost 50 irinum *

Katana: range 1 meter, damage; 3d6, type; light, cost 100 irinum

War Axe: range 1 meter, damage; 7d6, type; heavy, cost 120 irinum

Steam Hammer: range 1 meter, damage; 10d6, type; heavy, cost 250 irinum

Spear: range 3 meters, damage; 1d8, type; medium, cost; 20 irinum

Spiked Chain: range 3 meters, damage; 1d8, type; medium, cost 100 irinum

Plasma Gauntlets: range 1 meter, damage; 1d6, type; light, cost; 80 irinum

Starmetal Staff: range 2 meters, damage; 1d8, type; light, cost; 90 irinum

*Military Ordinance: Sold by few vendors
**Illegal to own: Sold in unknown locations, have a explaination of where you obtained this item in your backstory