Without ammunition your militia rifle becomes an expensive and not very efficient club. Availability, type, storage requirements, and cost are some of the many things you should consider concerning the ammunition necessary to accomplish your militia mission.
Availability. Political considerations can impact greatly on the availability of ammunition. There have been proposals in Congress to ban the sale of .25ACP, .32ACP and 9mm handgun ammunition since these are alleged to be the calibers of choice for criminals (even though the 9mm is a very popular police and self defense caliber and is the current standard handgun for U.S. armed forces). Taxes of up to 2500% for hollowpoint handgun ammunition have also been proposed. There are also efforts being made to ban handgun ammo capable of penetrating bullet resistant vests worn by police. Since single shot competition and hunting handguns have been made for most rifle calibers, such a ban would eliminate most rifle calibers. A proposed "arsenal" license would limit possession of ammunition to 1000 rounds, including primers for reloading. Congress doesn't even have to pass restrictive legislation to affect ammo availability. Hysteria over the effectiveness of Black Talon ammunition forced Winchester to stop civilian sales before a law was passed banning all hollowpoints. The anti-gun Clinton administration halted the importation of all firearms and ammunition from China by the stroke of a pen on an executive order. Similar action against Russian imports has been rumored and may have already been implemented. This has frozen the available supply of inexpensive 7.62x39mm ammo for AK and SKS type semiautomatic rifles. If your militia rifle is chambered for 7.62x39mm, you would be well advised to acquire and cache as much ammo as you can while it is still available. Actually this is good advice regardless of your choice of militia firearm, since any useful military caliber is a likely target for future anti-gun politicians to tax, limit or ban. To insure future availability of ammunition be sure to register and vote against anti-gun politicians who would restrict the Constitutionally guaranteed right to keep and bear arms. Using the ballot box now to protect our liberty might prevent our having to use the cartridge box later.
Ammunition Type. International law regulating armed conflict prohibits small arms ammunition designed to cause unnecessary suffering to the enemy. This means that military rifles used in warfare must use only full metal jacket or "ball" ammunition. Law enforcement and internal security use of softpoints and hollowpoints is not prohibited. The top U.S. military court has determined that hollowpoint ammo may be legally employed by soldiers against terrorists, so this should cover use by the Militia against the BATF Gun Gestapo or other agents of federal terror. Full power rifle calibers like the 7.62mm NATO (.308 Winchester) generally have enough stopping power when loaded with ball ammo. Loaded with softpoint or hollowpoint hunting ammo they are devastating. Intermediate power assault rifle calibers like 5.56mm NATO (.223 Remington) or 7.62x39mm are marginal stoppers with ball ammo, but are adequate with hunting type ammo. Match ammo is usually more accurate and is most often loaded with a boattail base bullet with a very small hollowpoint. These streamlined bullets retain downrange energy better and shoot flatter than standard flatbase bullets. However, match hollowpoints are not designed to expand like hunting hollowpoints and act like full metal jackets when they hit a warm-bodied target. Nosler Ballistic Tips are reloading component bullets that take a hunting hollowpoint designed to expand and fill it with a pointed plastic insert. Nosler Ballistic Tips are as flat shooting and accurate as most match bullets, but have the increased stopping power of a hunting bullet.
Storage Requirements. Basically ammunition must be stored in a cool dry place. Heat and humidity can degrade the propellant powder and lubricants (especially light penetrating types) can deactivate primers, so keep them all away from your ammo. Surplus ammo cans or waterproof plastic boxes with moisture absorbing desiccant packets are ideal for long term storage. Factory ammo has a shelf life of several decades and properly stored reloads will also last a long time. Military specification ammo usually has the primer sealed with lacquer and many use a lacquer or asphalt seal between the bullet and case neck. Primer sealants are also now available for reloading.
Cost. Since you should stockpile a large quantity of ammunition and should also get plenty of practice, ammo cost is likely to be an important consideration. Surplus military ammunition costs less than new factory ammo, but you have no guarantee that it has been properly stored. Sealed cans or plastic packs may have kept the humidity away, but just how long did it sit sweltering in some hot tropical third world warehouse? Many countries will dump ammo on the surplus market after testing has shown a particular lot to have degraded. Factory ball ammunition in case lots of 500 or 1000 rounds at discount prices is available in most popular military calibers from Federal, Remington, Winchester, PMC and Hansen. Factory softpoint hunting ammo is available at a higher price. Unlike much surplus ammo, factory ammo is usually made with reloadable boxer primed brass cases. If you have reloading equipment and purchase the cases and bullets in bulk, you can make softpoint or hollowpoint hunting type loads for about the same price as factory ball ammo. Powder and primers can be purchased cheaper locally, but two mail order sources for bulk quantities of cases and bullets are Midway (1-800-243-3220) and Dillon Precision (1-800-223-4570). Premium reloading bullets like the Nosler Ballistic Tip cost more but will give you much more effective and accurate ammunition. Bullets used in reloading for a semiautomatic rifle should have a crimping groove or cannelure to prevent bullet setback upon chambering, which can result in excessive pressures. The Lee factory crimp die will allow any bullet to be given a secure crimp and is available for most popular military calibers.
Special Considerations for Various Calibers:
7.62x39mm - If armed resistance against a future tyrannical government is ever required, don't count on resupply of 7.62x39mm ammo from raids on government arsenals, deserters or dead enemy troops. Most surplus 7.62x39mm ammo has been made with non-reloadable berdan primed steel cases. It would be a good idea to get reloading equipment and a sufficient quantity of components. Most military and factory loads for this caliber use .311" diameter bullets, but .308" bullets may be substituted so long as your reloading die has a .308" neck expander. Winchester sells bulk packed .311" 123 grain soft point bullets. The Nosler .308" 125 grain Ballistic Tip or Speer .308" 130 grain hollowpoint should give excellent stopping power.
5.56mm NATO - Original military load was the M193 Ball using a 55 grain flat base full metal jacket bullet fired from the M16A1 rifle with a 1 in 12" twist rate. The current U.S. military standard is the SS109/M855 Ball 62 grain boattail full metal jacket bullet with a steel penetrator core fired from the M16A2 rifle with a 1 in 7" twist rate. This same bullet is available as a reloading component as the Speer 62 grain FMJ. The rate of twist of the rifling of your barrel is very important when selecting bullets for this caliber. Original AR-15 rifles had a 1 in 12" twist and the Ruger Mini-14 had a 1 in 10" twist, while current manufacture uses a fast 1 in 7" twist. Bullets heavier than 55 grains will not properly stabilize in a slow twist barrel and will be inaccurate. A rifle with a 1 in 7" twist rate will be accurate with any weight bullet, but must not use varmint bullets with very thin jackets designed to explode on impact like the Federal 40 grain, Sierra Blitz or Hornady SX. Because of the extra centrifugal force imparted by the fast twist, these bullets are likely to disintegrate in midair before reaching their target. Empty cases for reloading and surplus or generic 55 grain ball ammunition is widely available, but you must shop around to find 62 grain FMJ military type ammo. Winchester and Remington both sell bulk packed 55 grain softpoint bullets and Winchester also makes a 64 grain softpoint. The 55 grain Nosler Ballistic Tip should give excellent accuracy and stopping power.
7.62mm NATO - This caliber was the U.S. military standard with the M-14 rifle and is still standard for the M-60 machinegun and for bolt action sniper rifles. The 7.62mm NATO is also a popular police caliber for SWAT team counter-sniper use. Besides surplus and generic ball ammunition, factory match ammo with 168 grain boattail hollowpoint bullets is also manufactured and softpoint hunting ammo is widely available. Bulk 147 grain FMJ and 150 grain softpoints are available for reloading, but perhaps the best component bullets for this caliber are the Hornady 165 grain boattail spitzer or the Nosler 150 or 165 grain Ballistic Tip. If money is no object, the best loads for this caliber are probably the Federal Premium or Winchester Fail-Safe hunting ammo. Bullets of 180 grains or heavier should not be used for two reasons; they are designed to expand at the higher velocities of a .300 Magnum and they can over-stress the operating rod on rifles like the M-1A.
Pistol Calibers - Reloading for a handgun or pistol caliber carbine allows you to stockpile a large quantity of effective defense ammo for a relatively low cost. Commercial hard cast bullets in boxes of 500 are relatively inexpensive for practice use, but making your practice loads with hollowpoints lets your stock of practice ammo double as a stock of defensive ammo at only slightly higher cost. Swaged lead semi-wadcutter hollowpoints are available in boxes of 500 for .38 and .44 caliber revolver reloads and jacketed hollowpoint bullets are also available in bulk quantities for discount prices. Premium hollowpoint bullets like the Speer Gold Dot or Hornady XTP should have better stopping power than bulk hollowpoints with the exception of the Winchester Silvertip. Casting your own hollowpoint bullets will insure that you will still have an available supply even if their sale is outlawed. The following example defensive handgun loads you might wish to try are taken from the Hodgdon 26th Edition Data Manual and use Hodgdon HS-6 powder: .38 Special +P, 110gr JHP, 9.8gr HS-6 or 158gr SWC-HP, 7.3gr HS-6 (these two +P loads should be used in steel frame guns only and result in comparable velocity to +P+ factory loads that are sold to law enforcement agencies only). 9mm, 115gr JHP, 7.0gr HS-6 or 124gr JHP, 6.8gr HS-6 (slightly hotter than factory loads). .45ACP +P, 185gr JHP, 10.0gr HS-6 or 230gr JHP, 9.3gr HS-6 (the Speer Gold Dot is probably the best bullet for these .45 ACP loads).