Not many companies that I know of make an AEG pistol, and the only one that I can think of doesn't have a working slide. If it is a gas pistol, it could mean that the mag is out of bb's so the slide locks back. If the slide is going back but the bb is not firing could mean that the gas isn't getting to the chambered bb. Not sure if this helps, but you may want to rephrase the question.
Rifles and pistols
Which pistol? Most production pistols have a barrel length of 1 to 8 inches.
It depends on the model. Rifles usually have one behind the barrel or under the barrel. Pistols may have one under the barrel or in the grip.
Information not in the public domain.
A magnet in the seat of the barrel
About 1937, but really depends on the model.
Muzzle
Cabela's sells some double barrel muzzle loading rifles. Pedersoli sells some double barrel muzzle loading pistols. You could also go to GunsAmerica.
Winchester made 2 air guns (pistols) the model 353 and 363. both are break barrel air guns. You said "Guns" so I assume you want pistols not air rifles. 1. Break the barrel down and push it all the way until it locks. 2. Load the pellet into the open breach at the barrel hinge. 3. Close the barrel back up. 4. Remove the safety. 5. Aim and fire.
IN A SHOT GUN, BUTTSTOCK, RECIEVER, BARREL AND FORESTOCK. RIFLE= STOCK, BARREL, ACTION, AND BOLT OR LEVER. IN A PISTOL= REVOLVER, WE HAVE BARREL FRAME GRIPS, CYLINDER AND TRIGGER. SEMI AUTO PISTOLS= SLIDE BARREL FRAME GRIPS, AND MAGAZINE OR CLIP.
It's under the cylinder swing near the barrel.
With very few exceptions (shotguns), most firearm barrels are rifled--even pistols.