firearms comparison:
The only examples of firearms that we have from the Goblin Earth timeline are a pair of "Beast's Teeth" pistols and a single "Serpent's Bite" shotgun. The Shotgun isn't anything special, 8 round revolver-style magazine, lever action and modified to be used 1-handed. Far more interesting are the pistols.
The pistols are constructed of steel with various brass rivets and lead solder holding them together. These softer connection materials cause tolerances are fairly loose similar to a Kalishnikov. The pistols are semi-automatic, with integrated 50 round magazines. Those magazines are held in place with a quick-release ejection clasp around a shroud. Diz has shown that with acrobatic training she's capable of "Juggle" reloading, allowing her to reload the pistols while holding the pistols in each hand. The high caliber rounds are designed for maximum impact, sacrificing range and penetration. Against an unarmored target the rounds are devastating, (in pig tests) flesh experiences horrible ruptures and massive exit wounds. Body armored targets are often knocked from their feet (according to Diz's testimony) where they can be safely detained or further fired upon. The barrel has a floating-bolt system to partially compensate recoil. Attached up top to the magazine shroud, the sight has a blade along the top for close combat. Easilly detachable with a quick-release. Diz pointed out that the original design called for a "ballistic-knife" system which she had removed due to the fact that it cooked off too often under hot situations.
**ADDENDUM**
The following information was obtained from Diz regarding other common weapons of both her own Empire and others within her home timeline.
Goblin firearms:
In addition to the two listed above.
Lightning rifle: The main battle weapon of the Goblin "Imperial Army". The Lightning is a 20 round bolt-action rifle, easily (and commonly) modified to be semi-automatic. The bolt-action can have a clockwork device added to it to cause this semi-auto modification to function. Many soldiers are considered too expendable to receive said modification, or choose not to use it to maintain stealth. The device apparently needs to be wound up to function and makes a ticking sound.
Needle Threader: Utilizing the goblins short stature, the Needle-threader is a 2-man operated sniper rifle about six feet long. One goblin sits in front and spots, using a shield as a bipod and cover. The one behind aims and fires the device. The rifle uses a round apparently filled with mercury although it can be loaded with an armor-piercing round instead. From Diz's description this not only serves as a sniper rifle but also their equivalent to an "Anti-tank" recoilless rifle. 12 rounds, bolt action, but compatible with the same modification to become semi-auto.
Heavy Support Weapon: Apparently a hand-cranked gatling gun. Maxim-style automatic machine guns are available but only for the "Hardsuit marines" as they require precisely machined materials, and are too heavy for regular troops. From Diz's description these "Hardsuits" are a sort of goblin magi-tech powered armor. Only the most elite soldiers are trained in their use.
Northern Elven firearms:
The Northern-Elves apparently use a number of very elegant and intricate weapons. Their ammo capacity is lower then Goblin firearms, however they are more precise and they are much more commonly trained in the "Pistolier's Dance" technique that Diz is. They favor twin revolvers, although apparently the "Beast's Teeth" goblin design cribbed a lot of notes from one of theirs.
Southern Elven firearms:
The Southern-Elves favor shotguns. Diz has described their squad-support weapon as being something akin to a gatling shotgun. They also favor suprise tactics and light skirmishes, luring their enemies out to get close enough to use those shotguns.
Orkish weapons:
Orks are apparently brutish and rarely use firearms. Preferring instead to charge their enemies with large numbers and smash their skulls open. That said, occasionally they will carry horribly inaccurate fully automatic weapons of unknown manufacture. Diz hasn't heard of anyone who's actually gotten shot by an ork, she theorizes that the weapon doesn't actually shoot bullets, but the orks enjoy the sound it makes.
Dwarven firearms:
Dwarves will almost always use single-shot explosive round weapons. Diz describes Dwarven Knights as having a squire go into combat with dozens of weapons since it's often quicker to toss them aside rather than reload them. The weapons make large explosions and are designed to do heavy damage to large numbers of people.
Human Firearms:
Humans are kings of jungle warfare according to Diz. They use lever-action rifles and a variety of revolver pistols, but their greatest strength comes in making reliable weapons. They also favor surprise tactics, and they've concocted some sort of man-portable flamethrower.
Demon weapons:
Diz was less than helpful about this. Apparently Demons "Grow" their weapons based on what they like to use. Thus the specs are less than helpful. Fortunately she says a majority of them would rather rip their quarry apart then shoot them.