An ammo box tells you five things that matter: the cartridge, the bullet weight, the bullet type, the velocity and how many rounds are inside. The cartridge decides whether it fits your firearm. The other four decide whether it fits the job.
Start with the cartridge
The cartridge name is the first thing to match, and it has to match exactly. Your firearm's barrel or slide is marked with the cartridge it's chambered for. The box has to say the same thing.
Some names look close and aren't the same. For example, 5.56 NATO and .223 Remington share the same outside dimensions, but they're loaded to different pressures and the chambers aren't identical. Which way you mix them matters:
- .223 Remington can be fired in a chamber marked 5.56 NATO.
- 5.56 NATO isn't recommended in a chamber marked .223 Remington only.
Always check your barrel's marking and the manufacturer's guidance. SAAMI, the industry's ammunition standards body, lists cartridge combinations that aren't safe to fire, and your barrel or ammo maker's instructions come first. When in doubt, ask us.
Grain is bullet weight, not powder
"55 gr" or "115 gr" is the weight of the bullet alone. A grain is a small unit of weight: 7,000 grains make one pound. It says nothing about how much powder is in the case.
Within one cartridge, a lighter bullet usually leaves the barrel faster and a heavier one usually holds its speed better at distance. Your barrel's twist rate matters here too. Faster twists stabilize longer, heavier bullets. If your manufacturer lists a recommended bullet weight range for your barrel, start there.
The bullet type abbreviations
The letters after the weight describe how the bullet is built. These are the common ones:
- FMJ (full metal jacket): a lead core with a copper-alloy jacket over the nose. Made for practice and training. It's usually the least expensive option.
- JHP (jacketed hollow point): a jacketed bullet with a hollow nose, designed to expand.
- SP (soft point): a jacketed bullet with exposed lead at the tip, designed to expand. Common for hunting.
- OTM (open tip match): a jacketed bullet with a small opening at the tip left over from how it's made. It's built for consistency, not expansion.
- 00 buck, #4 buck, #8 shot: shotgun loads, named by the size of the pellets inside. Lower numbers mean bigger pellets.
Pick the type for the job. Practice ammo for the range, and whatever your hunting regulations or intended use calls for when it matters. If a box doesn't say clearly what it's for, read the manufacturer's description of that load.
Velocity and the fine print
Velocity is printed in feet per second (fps). It's the speed the manufacturer measured from a test barrel of a stated length. Your barrel length will move that number up or down, so treat it as a comparison between loads, not a promise.
You'll also see a lot number printed or stamped on the box. Keep the box with the ammo. If a manufacturer ever issues a notice about a lot, that number is how you'll know whether yours is affected.
Round count and price per round
The round count tells you how many cartridges are in the box: 20, 50, 500 or a full case of 1,000. When you compare boxes, compare the price per round, not the price per box.
A good everyday pick for an AR-15 range day is a box of 5.56 NATO 55 gr FMJ. For a shotgun, look at a box of 00 buckshot.
Our ammo rules
When we have ammunition in stock, it's sold to adults 21 and older; you'll confirm your date of birth at checkout. Ammo ships by ground only, so it can't go to Alaska, Hawaii or a PO box, and some states restrict direct delivery. Your cart shows any restriction before you pay. See Shipping and State restrictions for the details, or check our ammo page for what's in stock.