Possible.
The same thing that happens whenever ANY firearm fires accidentally: The bullet will leave the barrel at a high velocity, and anyone/anything in that bullet's path will be hit. If there is anything flammable near the muzzle, it could catch on fire.
A hadgun that fires a .5" projectile
Generally it is a small concealable auto loading pistol of limited power. It takes its name from the .25 ACP cartridge that it fires. It is called .25 caliber (notice the decimal point?) since the bullet it fires is about 25/100ths of an inch in diameter.
It fires 5.7x28mm.
Noop. an M16 fires a 5.56mm (or .223 caliber) bullet. A .45 caliber shoots a bullet that is ~11.43mm.
Probably. It would likely refer to a handgun that fires a .45 caliber ACP, or .45 GAP or an older .45 caliber revolver round.
Assuming you mean caliber, the caliber simply refers to the diameter of the bullet the gun is designed to fire. American cartridge sizes are expressed as tenths or hundredths of an inch, and European cartridges sizes are expressed as millimeter. A .40 caliber gun fires a bullet that is .40 of an inch in diameter. A 9 millimeter gun fires a bullet that is 9 millimeters in diamter. There are too many variations to list here, but some common handgun calibers are 9 millimeter, 10 millimeter, .40 SW, .38 special, .44 magnum, .45 ACP, .380 ACP.
It fires a 22LR projectile. "Power" will depend on bullet weight and velocity.
It fires a 7.62x51mm NATO bullet, which is similar to a .308 Winchester.
Caliber refers to the diameter of the bullet the gun fires. The caliber of a 9mm is 9 millimeters. That is about .356 inches.
It is a self loading handgun that fires a bullet nominally 0.45 inches in diameter. Which there are numerous DIFFERENT .45 caliber pistols, the best known may be the 1911A1. Initially adopted by the US military in 1911, it served as the main US military handgun until recent years.
Some of the fastest- the Ruger .204, the .220 Swift, and the 30-06- but only if the 30-06 is shooting the Remington Accelerator. That is a sabot cartridge that fires a small .25 caliber bullet at roughly 4,500 fps.