I've fielded several questions from readers over the past months, partly prompted by my shooting-related articles, partly by my posts on emergency preparations (both categories are listed in the sidebar). The general thread of the questions has been "How much ammunition should I keep on hand?" That's a more complex question than it might at first appear. I'll try to address the various issues involved in this article.
Before we get down to the numbers, let's dispose of a few related issues. The first is the question of the needs or requirements for ammunition that one's likely to face. In this article, we're speaking as civilians, not as military or law enforcement personnel. The latter have their own needs and perspectives (expressed in military terms such as 'day of supply', 'unit of fire', etc. - for a classic definition of those concepts, see here). We're not planning for some sort of 'Red Dawn' scenario; nor are we trying to calculate how much ammo we'll need to survive the zombie apocalypse, or TEOTWAWKI, or December 21st, 2012! We'll discuss 'unforeseen circumstances' later, but basically, if the whole world goes to hell in a handbasket, we're probably all going to go with it! If you think otherwise, there's a bridge in New York City I'd like to sell you. I understand it has some nice hidden compartments that'll make great survival shelters! Going cheap!)
Second, there are legal and regulatory considerations to take into account. Some jurisdictions (State and/or local) have set limits on how much ammunition and/or reloading components may be kept in a domestic residence. Some also specify the type of storage required for it (usually as part of the local fire code or related regulations): depending on the quantities involved, they might specify fire-proof containers or even a stand-alone structure, which can get very expensive. Multi-dwelling buildings such as duplexes or condos, and some homeowner associations (HOA's), may impose conditions, rules or regulations governing the presence and/or storage of firearms and ammunition; if you rent, your landlord may do the same in your lease agreement. Failure to comply may mean eviction, and possibly civil liability for damages. Your insurance company may also impose restrictions on ammunition quantity and/or storage method(s), usually as (a) condition(s) of your policy. Check the small print carefully, because if you violate your policy's conditions, your coverage may be rendered null and void.
(This happened to a family I know. They suffered a fire in their home, which didn't involve the husband's [large] supply of ammunition at all; but the insurance assessor noticed it while he was inspecting the damage, and mentioned it in his report. The insurance company immediately denied the family's claim, on the grounds that their policy restricted the quantity of ammo that could be stored in the insured building. It didn't matter that the ammo wasn't involved in the fire in any way - the insurers were adamant that its mere presence was sufficient to render the policy null and void. Since the policy document did, indeed, include such a clause, the family's lawyer advised that their chances of successfully challenging their insurers in court were not good. Accordingly, he refused to take the case on a contingency basis - if they wanted to sue, they'd have to pay his fees up front. They ended up having to shell out almost $30,000 in repair costs, out of their own resources.)
You need to check all such laws, rules, regulations and conditions (and, if necessary, move to a new residence to avoid onerous condo/HOA/landlord's conditions of occupation, or switch to a more accommodating insurance company) before starting to build up your ammo stash. This applies particularly to rented accommodation and/or to a multi-dwelling building. If your ammunition stocks contribute to the destruction of other people's property, and/or are the cause of others being fined for a violation of the fire code or having an insurance claim denied on the grounds of a policy violation, rest assured - you will be sued to recover every cent!
OK. Having dealt with those background issues, let's look at how much ammo you need. I'm assuming that you've chosen a primary defensive weapon or weapons. You need enough 'carry' or 'defensive' ammunition to load it, plus have spare rounds on hand to reload it in emergency (either in spare magazines for a pistol or rifle, or speedloaders for a revolver), plus have enough in reserve that you can expend your 'carry' loads regularly and replace them with fresh rounds. I personally plan on shooting my 'carry' loads every quarter, and reloading my magazines at that time. I also want to have at least one year's supply of 'carry' ammunition on hand - preferably two years or more, because each production lot of ammunition may differ in velocity, point of impact, etc. Once I've become accustomed to a particular lot, I want to stick with it.
Bear in mind that 'defensive' ammunition is designed to dump its energy into one's target by means of post-impact expansion and/or fragmentation (link is to an Adobe Acrobat document in .PDF format) and/or tumbling. Such ammunition must be manufactured in such a way as to produce these effects, and consequently costs more to make (frequently much more) than standard 'solid' ammo. Unfortunately, if one wants top performance, one has to pay for it . . . and for defensive use, I want the best-performing ammunition I can get!
From here it's a matter of simple mathematics. Let me illustrate by taking five common defensive weapons as examples.
1. Smith & Wesson Model 686 revolver, caliber .357 Magnum. This holds 6 rounds in the cylinder. I usually carry at least one speedloader (commonly two) with 6 extra rounds apiece for rapid reloading. Let's assume two for this example. That means I'll have 18 rounds on my person when carrying the gun. If I replace them with fresh ammunition every 3 months, I'll need 72 rounds per year (assuming I don't need to shoot in self-defense, of course!). In a two-year stash of defensive ammunition, I'll need 144 rounds - or, more logically, 3 x 50-round boxes of ammo. At current prices for premium defensive ammunition, this will cost about $135.
2. M1911-type semi-automatic pistol, caliber .45 ACP. This pistol usually carries 7 or 8 rounds in its magazine, plus one in the chamber ready to fire. We'll assume you carry 7+1 in the gun, plus two 7-round spare magazines, for a total 'on-body' ammo load of 22 rounds. Replacing them every three months, you'll go through 88 rounds a year. A two-year supply of defensive ammo will thus involve at least 176 rounds, or 9 x 20-round boxes of ammo. At current prices for premium defensive ammunition, this will cost about $280.
3. Glock 19 semi-automatic pistol, caliber 9mm. Parabellum. This pistol holds up to 15 rounds in its magazine, plus one in the chamber. We'll assume you carry at least one spare magazine with the gun, for a total ammo load of up to 31 rounds. Replacing these four times a year gives 124 rounds, so a two-year supply of defensive ammo will be 248 rounds, or 5 x 50-round boxes. At current prices for premium defensive ammunition, this will cost about $150.
4. AR-15 type semi-automatic rifle, caliber 5.56x45mm NATO. The standard magazines for this weapon hold up to 30 rounds, although 20-round magazines are also fairly common. Furthermore, experienced users usually download the magazines by up to 10% to prevent feeding problems, so that a 30-round mag will normally hold 27-28 rounds. We'll assume you have one magazine in the weapon for home defense, with a single spare magazine available. Since you're presumably not carrying the weapon around with you, you won't expose the rifle to as much dust and dirt as a handgun, which means you can probably get away with replacing the carry loads only twice per year, for an annual total of about 120 rounds of defensive ammo. Since 5.56mm. ammo is usually sold in 20-round boxes, that means a minimum two-year stockpile of at least 12 boxes. At current prices for premium defensive ammunition, this will cost about $300.
5. Mossberg 500 pump-action shotgun in 12 gauge. The shotgun (in its standard model) holds up to 5 rounds in its tubular magazine, plus one in the chamber, and users will usually carry sufficient rounds for at least one reload (I prefer two) on their persons or in an ammo carrying device. That means at least 15 rounds in a combat load. Again, you probably won't carry this gun with you at all times, so the ammo won't be exposed to as much dirt and dust as a handgun's; however, it's plastic-cased, meaning that it's more easily damaged than metal-cased cartridges. I therefore recommend rotating shotgun ammo every three months, for an annual consumption of at least 60 rounds. Defensive shotgun ammo (buckshot and slug loads) is usually packaged in 5-round boxes, so that means a two-year stockpile of at least 24 x 5-round boxes. At current prices for premium defensive ammunition, this will cost about $160.
In the examples above, I've calculated minimum figures for a defensive ammo stockpile for each weapon. I'm an old-fashioned, take-precautions sort of guy - you know, belt and braces and a piece of string, that sort of thing. I won't go into details, but let's just say that I make sure to have several times more than those minimum amounts in my stash at any time! It's for you to make your own decision as to what meets your requirements. Choose wisely!
Of course, those figures are for high-quality defensive ammunition. You don't want to use that for routine target practice - it's much more expensive than plain-vanilla training ammo. Nevertheless, routine training is essential. Firearms skills are perishable. If you don't have specific training weapons available in a more affordable caliber (e.g. .22 Long Rifle, or .22LR), you'll need to shoot a minimum of 50-100 rounds, at least once per quarter, to maintain even minimal skills. Many experienced shooters expend that much ammunition every week, or at a minimum every fortnight. That's what it takes to maintain a high level of skill. Unfortunately, that's also very expensive. Some lower their costs by reloading their own ammunition. Others (including myself) use dedicated training weapons (or rimfire conversion kits for our standard weapons) in a low-cost caliber such as .22LR. At the time of writing, I can buy those cartridges in bulk for about 3½ cents each, compared to a minimum of 18½ cents per round for the cheapest, lowest-quality bulk 9mm. Parabellum training ammo. That means I can afford to fire over five times more .22LR rounds in training, maintaining a higher standard of competence and accuracy than I could afford to do with the more expensive caliber.
You'll probably find it cheaper to order your ammunition from an online vendor than to buy it from a local gunstore (assuming local laws permit you to do so - some jurisdictions discourage online ammo purchases). Online vendors also usually have a better ammo selection than small local shops. However, it's important to keep your local gunshop in operation, otherwise how are you going to get your hands on a gun if you need another one? It's a good idea to give a certain amount of your custom to local stores for that reason, even if their prices are a bit higher than online vendors.
I recommend giving careful consideration to where and how you store your ammunition. It's best kept in cool, dry conditions, free from humidity, and secure against prying fingers (particularly those of little children). Some shooters use steel office cupboards, removing the standard flimsy steel shelves and replacing them with a heavy-duty set of shelving capable of holding a lot more weight (ammo's heavy stuff, after all!). Here's an example of two ammo cupboards in one shooter's garage.
When the doors are closed and locked, little fingers can't get into anything dangerous; and opportunist burglars are unlikely to give old, battered-looking steel cupboards a second glance.
I mentioned earlier that we'd discuss 'unforeseen circumstances'. We're in the middle of one such circumstance now - a general shortage of firearms and ammunition for the civilian market in the USA. This is not, repeat, not the result of deliberate government policy, or an evil, sinister conspiracy to deprive us of our Second Amendment rights, or anything like that (despite what alarmists would have you believe). It's the result of a considerable expansion in firearm sales over the past few years, partly driven by political uncertainty, partly by the spread of legislation permitting concealed carry of firearms and other supportive measures. Large government purchases (such as this recent contract) add to the consumer's pain, because manufacturers will devote their primary attention to filling such profitable orders. You can read more about the current ammo shortage here and here. Whatever the cause, it means that right now, if you want premium defensive ammunition, you may not find it very easily - and when you do, its price may be significantly higher than you expect to pay. Far better to stock up when you can afford it, and buy enough to keep you going for a while. That way, you won't have to buy at 'panic prices' if you run short. If you need some right now, I'm afraid it's going to cost you more.
Another unforeseen circumstance might be the need to supply your friends and others in an emergency. I've written previously about my experiences after Hurricanes Katrina and Rita in 2005, and following Hurricane Gustav in 2008. Part of that was being asked by visiting friends to supply them with additional ammo, as they didn't bring much with them. Fortunately, I had enough in my stash (in the right calibers) to be able to help them, without running short myself; but you may be sure I pointed out to them the need to increase their own stocks before the next disaster hit!
A final consideration. Weapons and ammunition (particularly adequate supplies of both) are like a parachute. It's better to have it and not need it, than to need it and not have it! The same applies to sufficient training and practice to be able to use your weapons and ammunition effectively, if the need should arise. It's too late to start learning when the proverbial brown substance hits the rotary air impeller!