"Which caliber would you recommend?" is a question we get a lot, from our customers.  While there is no right answer, and experienced shooters will probably give you 100 different answers, here are some points to consider when deciding what caliber is right for you.

1. Do you have guns in particular caliber already?  The answer to this question could steer you either way, but at least it may help narrow the choices.  Some people may choose to stick with the same caliber, if for instance their spouse already has a gun, in order to keep only one type of ammo around.  Home-defenders and survivalists might choose to stick with the same caliber to make ammo interchangeable during an emergency.  Other people might select a different caliber, to mix things up and experience something new.
2. Are you purchasing a specific model firearm?  Most models of guns only come in a few, or one, chamberings.  Deciding which model you like best may make the choice of caliber significantly easier.  If the specific firearm you want doesn't come in your favorite caliber, a competing manufacturer probably makes a very similar gun that may be available in a caliber you like.
3. Get the biggest caliber you can shoot comfortably.  For many purposes, such as personal defense, bigger bullets are more effective, or at least encompass a larger range of uses.  The corollary to this principle is "Don't buy a caliber larger than you can shoot comfortably."  Trying to find the largest caliber you can shoot comfortably, without going over, can narrow down a small range of options.
4. Stick to popular military cartridges.  Military chamberings become very widespread, resulting in more available, less expensive ammo.  This is not only true of current ammo, such as 9mm NATO or 5.56mm NATO, but also old favorites such as the venerable .30-'06 (a favorite of hunters for over a century).
5. Avoid new or exotic rounds.  Sure, that .50 Desert Eagle or 6.8mm SPC rifle look cool, and you read all the rave reviews on internet forums, but ammo for them is expensive and difficult to find.  I've had more than a few customers come in looking for bizarre ammo for a revolver, that never gained the popularity originally promised.
6. Obey Hunting Laws.  In many states, including Colorado, there are legal requirements as to what minimum calibers of gun can be used to hunt certain game.  If you plan to hunt, especially a certain animal, meeting the legal stipulations can help eliminate a range of unsuitable calibers.
7. How big is your hand?  In semi-auto handguns, the size of the grip frame is directly related to the size of the magazine and bullets.  While there are single and double-stack magazines, if you have small hands, you'll generally need to stick with smaller cartridges.
8. You can carry more small bullets.  If you're planning on shooting at prarie dogs all day, or wading into a zombie apocalypse, more ammo is a big advantage.  The smaller the round, the more you can carry with you.  Strike a balance between carryability and ballistic energy to meet your needs.