Lots of bad info. Tons, in fact. Every other sentence, almost, not counting the rampant use of "bullet," "clip," etc.
Mateba cylinders swing down like any old revolver. Only the one in the anime swings up.
Almost all derringers use tip-up barrels. A few (mostly single shot ones) swing to the side instead. Almost none are breech loaded. The Liberator and the Deer Gun are the only breech loaded guns I can think of, and they aren't exactly derringers.
Standard C96 Mausers were not available in full auto, that was the C-96 model 712, which used a detachable magazine, and were only produced in
very small numbers.
Full moon clips are
not the same thing as speedloaders. Speedloaders release the rounds after they're loaded. Moon clips stay attached, and go in the gun with the rounds.
.45 Long Colt does
not give "similar ballistics to magnum ammo." Standard .45 LC is more like .45 ACP. Low pressure, low velocity. There are some "Ruger only" loads that get pretty hot, but those will destroy a weaker gun.
Having the barrel on the bottom chamber will
not make the gun recoil down. The bore axis is only moved down about as low as the bore axis on a Glock. The barrel would need to come out the bottom of the grip for the gun to recoil downwards.
Since when are deer "large game?" Large compared to a bunny, maybe.
A long barrel does not increase inherent accuracy. Actually, long barrels are inherently
less accurate than a barrel that's identical in all respects other than length (up to a certain point), because of vibrations. About 1 to 3 inches is the "ideal" barrel length for pure accuracy, since that's all that's necessary to stabilize the bullet. Of course, velocity would suck.
P90s are prized only by weird people. The 5.7mm's penetration is "formidable" only when compared to pistols. Absolutely any real rifle blows it away.
MGLs typically do not use double action triggers. They're single action, with a spring powered clockwork type action rotating the cylinder immediately after a shot is fired. Usually, anyway.
Only some compensators have ports that point up only. It's very common for compensators to have holes all over the place. Most muzzle brakes for high powered rifles have ports that point directly to either side. It's a myth that the port direction makes any difference at all. Compensators reduce recoil mostly because of transferred momentum of propellant gas smacking into the leading edge of the compensator. Also, they can increase accuracy because gas is blown off to the side, instead of directly behind the bullet.
True double action only guns can fire if dropped, if they have no firing pin safety. Either inertial discharge by dropping barrel first (off a two story building), or discharge by dropping on the hammer, if it doesn't use an inertial firing pin.
Yeah, right, you could hit a zombie in the head with the first shot, because the gun's that accurate. I want a gun that's so good it'll make me actually shoot better. Also, if de-cocked, Berettas have about an 18 pound trigger pull for the first shot. That's 8.16 kilos, or 80 Newtons.
Since when are M4s not high stopping power? 5.56mm is great at close range, even from the short M4 barrel.
Recoil on AR-15/M-16 type pistols is extremely low.
http://www.gunblast.com/images/Bushmaster-Pistol/Mvc-017F.jpg
"it's likele it also has a small rocket moto to help propel it." Dude, why do you think they're called
rocket propelled
grenade launchers?
"Hammer down speed?" What the hell? Just the type of hammer makes no difference to hammer velocity. Commander style "ring" hammers are not inherently lighter than standard hammers.
Do those people actually think that kind of thing is possible?