Most guns in the Plux Galaxy are rune guns. A rune cut into the barrel turns crystal power into a hot metal bolt. A small aether crystal sealed in a brass case, called a crystal cell, powers the gun. A few old powder guns are still around too.
The rune guns are the rune pistol, the hand cannon, the rune rifle and the scattergun. They are martial ranged weapons and use Dexterity for attack and damage rolls. They have the Ammunition property, but they never have the Loading property. A character with Extra Attack can fire a rune gun once for each attack.
Rounds. One round is one shot. A full crystal cell holds a set number of rounds for each gun.
Rune pistol. Rounds per Cell: 20. Time to Change a Cell: Bonus Action.
Hand cannon. Rounds per Cell: 10. Time to Change a Cell: Bonus Action.
Rune rifle. Rounds per Cell: 20. Time to Change a Cell: Action.
Scattergun. Rounds per Cell: 10. Time to Change a Cell: Action.
Ammunition. Each attack with a rune gun uses 1 round from the cell in the gun. When a class or a start pack gives "rounds", those are rounds in crystal cells. For example, 40 rounds for a rune pistol is two full cells. Rounds are used up when fired. Unlike arrows, you can't recover them after a fight.
Changing a Cell. When the cell in a gun is empty, you must change it before the gun fires again. Changing a cell takes the time shown in the table. You need a free hand and a fresh cell. If you change a cell that still has rounds in it, the rounds stay in the old cell for later.
Empty Cells. The crystal in an empty cell turns grey. An empty cell can be refilled. See the Aether Crystals and Money rule.
Hand Cannon. The hand cannon kicks hard. If your Strength score is lower than 13, you have Disadvantage on attack rolls with it.
Scattergun. Being within 5 feet of a hostile creature does not give you Disadvantage on attack rolls with a scattergun.
No Misfires. A working rune gun does not misfire or jam. A gun stops only when its cell is empty, black or broken.
Black Cells. A crystal touched by the Vhal turns black and holds no power. A black cell gives no rounds and no charges. A gun loaded with a black cell does not fire. The attack is lost, and you must change the cell.
Noise. A rune gun shot is loud. Creatures within 300 feet hear it unless something louder covers the sound.
Crystal cells power more than guns.
Shock baton. One Cell Gives: 10 charges.
Crystal lance. One Cell Gives: 10 charges.
Rune lamp or brass helmet lamp. One Cell Gives: 24 hours of light.
Air bubble charm. One Cell Gives: 1 hour of air.
An item with charges spends 1 charge each time its text says so. Changing the cell in one of these items takes an action.
The pistol, the musket and the blunderbuss are old guns that burn black powder. They use the normal rules for the Ammunition and Loading properties. They fire firearm bullets, not crystal cells. Because of the Loading property, you can fire only one shot from them with each action, bonus action or reaction, even with Extra Attack. Rain or water ruins loose powder. A powder gun that gets soaked can't fire until it is dried and cleaned, which takes 10 minutes.
Keep track of full cells as items in your gear. Keep track of the rounds left in the cell that is loaded in each gun. When the last round is fired, the empty cell goes back in your pack.