Just because they have similar outside dimension doesn't mean they are the same.

One of those ongoing debates in the shooting sports world is whether or not you can safely interchange .308 Winchester and 7.62 NATO rounds.  The answer is "yes, but not really". 

Unless you have a good reason - you shouldn't.  Saving a few bucks is not a good reason.  ALWAYS shoot ammunition that matches the rifle EXACTLY.  There are various differences between 7.62 chambered rifles and .308 chambered rifles.  In a nutshell, the NATO chambers are built with a higher degree of tolerance to allow for ammo manufacturing variance - i.e. ammo could come from any factory from any of the NATO countries. 

The NATO rounds have a thicker case.  That means if you're into reloading your ammo (or buying the cheaper remanufactured ammo)  there is a fair chance that you will run into over-pressure   Under the wrong circumstances, that could result in a "spontaneous disassembly" of your firearm.  In layman's terms, your gun will blow up in your face as you're pulling the trigger.  That's not a good look, my friend.  Mind you, the same round would have been fine in a .308 chamber.  Here's a visual aid as to why it's especially bad to shoot .308 ammo out of your NATO chambered gun.

Take a look at the difference in chambers for the NATO (military) 7.62 and the commercial .308 Win.  The NATO chamber is roomier to account for variance in ammo dimensions.  Again, Military cases are also THICKER, which means they are able to better contain the pressure inside the cartridge without having to rely as much on the chamber to contain the expanding case during powder ignition.

.308 brass is thinner by comparison, but the chambers are tighter, so the case is less likely to burst inside the chamber because it is being contained.

Most of the time, you can get away with shooting 7.62 in your .308 chambered rifles.  Most of the time - if you're into playing the odds.  However, you should never shoot a .308 round out of your 7.62 NATO chambered rifle.  You'll probably get away with it for a while, but eventually something bad will happen.  Ammo is manufactured in lots of different places and by lots of different companies.  It's not entirely impossible to go to your local sporting goods store, grab a box of ammo that looks like a brand new factory load, but is in fact a "remanufactured" round with nice commercial packaging.  Remanufactured refers to the fact that the brass cases used in the cartridges have been fired once before.  That means the brass has been re-worked and probably weakened to a degree. 

This is a photo of some boxes of remanufactured ammo.  If you don't read the fine print, it might be easy to miss.  Just 'cause the brass is shiny doesn't mean it's new.  All I'm trying to say here is that it's not that hard to inadvertently pick up reloaded ammo.  Not all reloaded ammo comes in zip-loc bags from the local gun show.

Here's a good recipe for disaster and probable horrific injury:

1. NATO rifle, which by design uses the outside limit tolerances for chamber dimensions.  Again, this is to accommodate ammo from a large variety of international manufacturers.

2. A high velocity or remanufactured round of .308.  The case is weakened slightly and/or the powder charge is high.  .308 brass is already thinner before it's been fired even a single time.  A reloaded round of .308 is even worse off.  In practical terms, this means the case of your round will expand more easily and to a higher degree than a comparable round of 7.62mm.

Once you squeeze the trigger on that baby, your case will expand into the relatively large chamber and may burst INSIDE your firearm.  Hopefully it doesn't take all of your face with it.

You can be safe and save money by shooting reloaded .308 ammo out of your .308 chambered rifle - even the hotter loads.  If you're reloading your own ammo, you could also (obviously) modify the powder charge in your .308 reloads if you intend on shooting them out of a NATO rifle, but that's just asking for trouble.

In short, don't shoot ammo that's not designated for your chamber.  Stick to that, and you'll be able to safely enjoy your sport. :)

In part 1, we talked about the parts of a firearm cartridge.  Let's now take a (simplified) look at how these parts work together.  As it were, this little investigation will also show us why a cartridge going off without the benefit of a firearm isn't as dangerous as one might first think.

Most modern firearms have a hammer of some kind.  The hammer is the thing that makes the neat "cocking sound" when you pull back on it with your thumb.  When you pull the trigger, the hammer is propelled by a powerful spring and eventually hits a "firing pin".  The firing pin is little more than a small metal rod who's job in life it is to hit the primer on your cartridge.  In older firearms, the hammer used to come into direct contact with the cartridge, but this is no longer done.

Once the firing pin on your firearm hits the primer on your cartridge, the primer explodes.  This, in turn, sends a tiny column of fire into the portion of the case that is holding the powder. 

Gun powder comes in many varieties, each having a different set of properties.  One of the most important factors is the burn rate.  You see, gun powder is designed to burn gradually as opposed to creating a big "flash" ignition.  Why is this so?  Here is where we get into the nitty gritty of how bullets work.

As the powder burns, pressure inside the case is gradually increased.  In fact, the case actually expands until it fills out the space inside the firearm from which it is being shot.  Eventually, the bullet breaks free of the case, with the powder still burning and steadily increasing the pressure.  Since the case is securely held in place and is surrounded and enclosed by the firearm, the pressure building in the case has no other way to escape except down the barrel, ultimately pushing the bullet out at incredible speeds. 

All of this basically works because of a thing called Newton's Third Law Of Physics.  With that in mind, let's say you get unlucky enough to set off a cartridge on accident by dropping it on something just right, or inadvertently striking it with something - what happens?

First, the primer explodes.  No two ways about it.  This, inevitably, will ignite the powder.  Now, the pressure inside the case begins to build.  Next, one of several things will happen (depending on a combination of the weight of the bullet, the structural integrity of the case and the type and quantity of powder used in the cartridge). 

The first thing that might happen is that the case ruptures (tears) and the gases created by the burning powder escape more or less uninterestingly. The bullet may or may not be flung about, but most likely not with lethal force.  Remember - the reason bullets fly to darn fast is that the pressure from the burning powder is channeled very directly behind the bullet traveling down the barrel.

The second likely thing to happen is that the pressure increases until the bullet is freed from the case.  Again - due to lack of a barrel channeling the pressure, the pressure will just escape the cartridge more or less uninterestingly.  Make no mistake about it, there will be a loud crack and you will likely feel a tiny shock wave from the explosion, but it will not be focused. 

In both of these scenarios, the energy from the burning powder is more likely to fling the case, rather than the bullet, around.  This happens because the case is lighter than the bullet and is easier to move.  Since the case isn't being held in place by the firearm, the force of the explosion is free to move it about.  Of course, a brass case flying around at incredible speeds can can still be dangerous, but nowhere near as dangerous as a bullet coming out of the business end of a gun.

Remember seeing those movies where they drop a bunch of ammo in a fire only to have bullets whizzing around in every which direction?  While entirely unsafe and dangerous (i.e. don't be an asshat and try it at home), that scenario is probably more fiction than fact, even if it would be extremely disturbing and scary.

So there you have it.  Try not to drop your bullets (cartridges) on the ground.  If you do, however, just remember that even in the unlikely event that you do set off the primer, you'll probably be okay.  Stay calm and don't pee on yourself - 'cause that's not a good look!

Remember to wear safety glasses and clothes that cover you up when you go shooting.  Even if nothing ever goes wrong, ejected cases are damned hot and WILL give you nasty burns that WILL leave a scar (especially if they happen to fall down the shirt of your female companion where the case isn't immediately retrievable - don't ask).

When dealing with firearms, one inevitably needs to deal with bullets.  Technically, guns aren't dangerous - bullets are.  That being said, as long as you treat ammunition with the same respect that you treat, say, electricity - you'll be fine.

So let's say you're at the range handling a fist full of large .45 caliber ammo and one tumbles out of your hand (in slow motion, 'cause everything is scarier in slow motion) and heads straight for the gravel floor beneath your feet.  A particularly pointy and mean looking pebble briefly glistens in the light of the afternoon sun and you just KNOW that round is going to hit that evil pebble square on the primer...setting off an inevitable chain reaction that will result in your or someone else's head being blown off by a stray bullet that you careless failed to hold on to. Every muscle in your body instinctively tightens in anticipation of the inevitable...

*CLINK*

Nothing. 

Phew!  It didn't happen - that time.  That was dangerous... or was it?

Actually, it is possible to set off a round with something other than the firing pin in your firearm - like a pointy rock or a hammer, or heat.  And while you shouldn't be setting off ammo without the benefit of a firearm, it's not as dangerous as you might expect.

In Part 2 of this post, we'll take a simplified look at the internal ballistics of how ammunition works.  First, however, let's take a look at the parts of a modern cartridge (picture borrowed from HowStuffWorks.Com).

The whole thing is called the "cartridge".  It's called that because it contains several parts.  As a matter of convenience, you can order a box of "bullets" at your local gun counter and everyone will know what you're talking about, even if it's not technically accurate.  Nobody buys a box of "cartridges".

The outer hull of the cartridge that contains all the other parts is called the "case".  This is the part of the cartridge that gets spit out of the side of your firearm after you pull the trigger. 

The very top portion of the cartridge is the "bullet".  That's the part that comes flying out of the front of your firearm after you pull the trigger.  The bullet is literally stuffed into the case and crimped into place during manufacture.  There's nothing else holding the bullet in place except the case hugging it snugly there.  It is, in fact, possible (and even common) to disassemble a cartridge by manually pulling the bullet out of the top.  In an emergency, this could be done with a pair of pliers but this is dangerous and can cause serious harm to you or others nearby.  Under normal circumstances you want to use an actual bullet puller.

Just beneath the bullet, is an empty space filled partially with the propellant.  The propellant is normally some kind of gun "powder".  It's the powder's job to create the pressure required to propel the bullet out of your firearm.

The powder is worthless unless you can ignite it somehow.  That's the job of the final component of our cartridge: the "primer".  Incidentally, the primer is the most unstable part of the bullet (much more unstable than the powder, actually).  The primer's job is to explode when it receives a sufficiently forceful whack.  Under normal circumstance, it's the firing pin in your firearm that does this.  If something else hits it hard enough, however, it will ignite just as readily. 

In part 2, I'll take a look at how all of the components of our cartridge work together to do its business.

Without ammunition, your firearm is just a heavy stick.  Ammo matter less if you're just at the range plinking for fun.  However...

When it really counts, like in personal defense type situation, you want ammo you can rely on.  For the longest time, Hydra-Shok seemed to be at the top of the market for self-defense ammo.  A new leader seems to have emerged with Texas-based RBCD (http://www.rbcd.net/).  The RBCD "smart" ammo is said to be a "blended metal" round.  The bullet will only deform and expand when heat is applied to it. 

In practice, it means that the bullet will punch through metal (like a car door, for instance) but will not over penetrate a piece of dry-wall.  That's a huge benefit for a self defense round.  One of the things you need to be most aware of when firing a gun or rifle is not only hitting your target, but being aware of what is beyond your target.  Ideally, your bullet should never over-penetrate your target so that there is no chance of hitting any unintended objects/subjects.  If you load your home-defense firearm with bullets that don't penetrate dry-wall, you have less of a worry of accidentally hitting little Jimmy next door instead of the murderous thief that just broke into your home.  Controlled penetration (as well as other factors) is one of the reasons why some people choose shotguns as their primary home-defense weapon (buckshot has less of a chance of punching through exterior walls).

The way the RBCD round works, in a nutshell, is that when it comes into contact with materials that wick heat away from the bullet (I.e. metal conducts heat way) it stays intact because the bullet stays relatively cool.  On the other hand, when it comes into contact with a material that concentrates the heat around the bullet (like drywall, or that home invading murderous thief) it immediately expands to enormous proportions, thus transferring maximum amounts of energy to the target. If your bullet goes clear through your target, much of the bullet's kinetic energy will not be transferred to the target.  In a self-defense type situation, you want stopping power, and stopping power is highly dependant on kinetic energy transferred to the target.

Check out this video for more info on this RBCD round.  It's pricey, but hopefully you'll never have to buy these beyond the occasional test round for the range (you should test your firearm with every type of ammo you intend on carrying it with).  I've put a fair amount of .45 RBCD through my HK USP CT.  I've never had any kind of jam or other failure.

Use the cheap stuff for target practice and plinking. Use RBCD when your life or someone else's depends on it! 

Being German, I know first hand the wonders of German engineering.  Everything that German engineers touch, turns to gold (that's right, I said it).  Naturally, firearms are no exception.  When it comes to handguns, I prefer H&K over any other manufacturer.  The weapons seem balanced and sturdy.  Most importantly - I can count the number of times that I've had an H&K jam on me on one hand. 

Of course, I shoot primarily .45 caliber semi-automatics which tend to have less of a tendency to jam simply because the magnitude of the force imparted on the slide is enough to keep things moving along.

My favorite C&C firearm has been the H&K USP Compact Tactical.  It's the little brother of the full sized USP.  The frame is more compact (obviously), but it still retains many of the other awesome USP features - threaded barrel (not that the average joe would use it, but it does have a "cool factor" to it), large trigger guard, ambidextrous  safety and a de-cocker that I use ALL the time (push the safety all the way down and the hammer drops safely).

This firearm is also superbly balanced and weighted.  It handles .45 caliber loads remarkably well for a compact, and all without wrecking my wrist.