Quoted: Ok, bear with me, I have a general knowledge of firearms but I've got a lot of questions.  Any help is appreciated. I've heard of people firing different caliber cartridges in their guns than the gun was originally intended for, like a .357 in a .38 and so on.  How is this possible?  Doesn't it damage the gun?

It's the other way around; people firing .38s in a .357.  Despite the names, they both use the same bullets, which are .357" in diameter.  Originally, people used to load .38 rounds VERY hot, and could use these only in certain models of (at the time) modern Smith & Wesson revolvers that were built very strong.  Eventually, these hot loads were standardized as the ".357 Magnum", and the case was extended a bit to prevent them from fitting into older, weaker .38 guns.  But it is very common for .357 owners to use the slightly shorter .38 rounds in their revolvers, as the .38s have less recoil and cost less.

What does P and +P mean?

+P and +P+ are indicators that the loads in question are loaded hotter than normal specs.  SAAMI, the organization that creates the industry standard pressure levels for factory cartridges, only lists pressure specs for three +P rounds [9mm +P, .38Spl +P, and .38Super +P], and NONE for +P+ rounds.  So, any load with a +P or +P+ marking is loaded to higher pressures and velocities than "SAMMI-spec" cartriges of the same caliber.

Is there any diffence in performance between left and right hand twist rifling?

No, but there may be reasons to choose one over the other.  For example, suppressed guns need to be threaded the opposite direction of the barrel twist, or the suppressor will tend to come unscrewed when you fire the gun.

Why are some bullets larger than others but marked as the same size?  (like a .303 being a .300 in diameter) And how much does this affect performance?

Caliber names are more like "brand names" than true measurements.  For most cartriges, you have to know the history of how it came about to understand how it came to be named what it is.  Often, a different number will be used to avoid confusion with a similar, older cartridge, even though the number isn't related to the actual measurement of either the bullet or the bore.  And, BTW, .303 British bullets are actually .311" in diameter.

When a bullet impacts something living, is it the kinetic energy of the bullet being transferred to the target that kills it, the hole/wound it inflicts or the actual damage to organs?

The short answer is: it's the wound damage, and resulting blood loss, that causes a person to go into shock and die.  If all it was was kinetic energy, then ballistic vests wouldn't work, because your body still absorbs the kinetic energy of the bullet when you're shot while wearing a vest.

If it is the kinetic energy that's most potent, why is the AR-15 so widely used?  A small caliber weapon with a high velocity will give you maximum penetration but not leave a very big wound or transfer energy to the target.

Start here: www.ammo-oracle.com

Can you use blackpowder in all weapons where it is safe to use smokeless powder?

No.  Black powder creates a very different pressure curve, which could blow up a gun.  Also, it will also gum up the gas systems of any semi or full-auto gun very quickly.

Who came up with the idea of making a gun out of plastic and why the hell would anyone want to do that?

For many components of a gun, plastic is ideal.  It is light weight, doesn't rust or corrode, doesn't get too hot or cold to touch, lasts longer (aluminum and steel frames often crack long before a plastic frame), and is much cheaper to produce.

What exactly is 'ball' ammunition?

"Ball" in this context is synonymous with "standard", and usually refers to standard, common FMJ rounds, as opposed to hollow points, tracers, or other speciality rounds.  The term comes from back when conical bullets were first used in guns originally designed for round balls.  When you shot "ball" ammo, you were shooting "standard" ammo, as opposed to the then-new conical bullets.

Why are pure lead bullets almost never used any more?

Lead bullets are still very common, but lead bullets require lube to reduce "leading", or leaving lead behind in the barrel, and the lube is smokey and dirty.  And, there will still be lead left behind.  Plus, lead bullets have an upper velocity limit that, if exceeded, will melt the lead and will leave big coatings of lead in the barrel, as well as allow the gas to blow around the bullet and slow it down.  Finally, lead shavings aren't good for the gas systems in semi-autos.  These days, we've made it easy to copper-plate lead bullets, so plain lead is becoming even less popular.

When using most semiautomatic pistols, does changing ammunitiion type/brand usually require changing to a different type of magazine and swapping out a few springs to better accomidate it?

No.

Why do some types of ammo produce more muzzle flash/noise in the same gun?

Different loads use powders of different brands and burn rates, and some are loaded to mild pressures and velocities, while others are loaded much hotter.  Hotter loads will generally have more blast and flash compared to the same powder loaded lighter, and different powder types will have more blast and flash than other types.

-Troy

The term "ball ammo" has been around FAR longer than the 60s, and describes the bullet, not the powder.  There certainly WAS a powder issue with early M16 ammo in Vietnam (I cover this in the Ammo Oracle), but this term predates that by over 100 years.

In fact, I remember seeing it in a book about WWI, written in the late 20s.  I'm trying to remember the title, as the book is in storage at the moment.  If I remember it, I'll add it to this thread.

-Troy

Originally Posted By Anyway, I just saw a Hornaday ad where it showed a .308 bullet that had been fired from a .30-06.  So this means the bullet was .308 in diameter but was fired from a .30-06 (the type of weapon, not nessecarily the caliber?) and the .008" difference in diameter was not significant enough to matter?

Again, the NAME of a caliber (".270", ".30-06", ".223") is really a marketing name, and should NOT be assumed to indicate the precise diameter of the bullet it fires.

For example, the ".30-06" name is really a shortened version of "30 Caliber, Model of 1906".  The rifle it was first fired out of, the 1903 Springfield rifle, was a "30 Caliber" rifle.  The barrel was made by taking a piece of round stock and drilling a hole in it lengthwise.  The hole itself was exactly .300" in diameter.  Then, the rifling grooves were cut into the barrel, about .003-.004" deep.  If you measured the barrel diameter at the lands (the high points), the diameter was still .300", but if you measured at the grooves, the diameter is .306-.308".  Pretty straightforward, right?

In order for the bullet itself to get a good seal in the barrel, and for the rifling to get a good grip on the bullet, the bullet's diameter has to be larger than the bore diameter (the measurement between the lands), but can't exceed the diameter between the grooves by much if any.  So, the bullets were made to be .308" in diameter.  Still, the NAME of the cartridge was not ".308-06", but ".30-06".  Why?  Because the rifle was still considered a "30 Caliber", and manufacturers don't worry much about being technically correct with their caliber names.

Later, in the 50's, the military decided to use the newer powder technology to reduce the size of the .30-06 round, which they could do without significantly changing the power of the round, due to the more efficient powders that were available.  They ended up shortening the .30-06 case by about .5".  By this time, NATO had been formed, and metric designations were in, so this round was given the military designation of "7.62x51mm NATO".  Winchester, who had helped to develop the new cartridge, named the cartridge ".308 Winchester".  Note that BOTH .30-06 and .308 use the identical diameter bullets.  ".308 Winchester" is just a marketing name, though in this case, it happened to be technically correct.

Another is ".223", which was based on the ".222 Remington" and the ".222 Remington Magnum", all of which use .224" bullets, as does ".22-250" and many others.  Again, the cartridge name is just a marketing name.

A reloading manual will give you the actual bullet diameters of most common calibers, most of which you'll find don't match their names exactly.

As for your other questions:

MOA means "minute of angle".  A circle is divided into 360 degrees, and if 1 degree isn't a fine enough measurement, then each degree can be divided up into 60 minutes, and each minute into 60 seconds.  Obviously, these are very narrow angles.

So, 1 MOA (minute of angle) is 1/60 of a degree.  At 100 yards, 1 MOA will be a circle of 1.04".  At 200 yards, 1 MOA will be a circle of 2.08".  At 500 yards, 1 MOA will be a circle of 5.20".  And, 3.5 MOA at 200 yards will be a circle of 7.28".

So your rifle and your ammo together can shoot 10-shot groups at 500 yards that measure 5.20" or less, your rifle is "minute of angle accurate" at 500 yards.  (Most of us round the 1.04" down to 1" per 100 yards.)  MOA is used as a short-hand method of describing a rifle/ammo's accuracy.

Ballistic coefficient is really the "coefficient of drag" that a given bullet has.  A bullet's shape and size will determine how much drag the bullet has, and there are formulas to express that drag as a number.  The larger the number, the less drag the bullet has, and the slower the wind will reduce the bullet's forward speed.  This number is needed to calculate a bullet's trajectory, which is needed to know how to adjust your aim (or your aiming device) to ensure you hit your target at different distances.

-Troy