The New Gun Owner's Complete Ammo Guide

You just bought your first gun. Now you need ammunition — and the options are overwhelming. Walk into any gun store or browse any online retailer and you'll see dozens of abbreviations, grain weights, bullet types, and price points that make zero sense to a new buyer. This guide walks you through everything from identifying your caliber to placing your first online ammo order.

This is the guide we wish existed when we started. No jargon without explanation, no assumptions about what you already know. Just a clear path from "I have a gun" to "I have the right ammo loaded and more on the shelf."

Step 1: Identify Your Caliber

Your firearm is chambered for a specific caliber — a specific size of cartridge that fits your gun's barrel and action. Shooting the wrong caliber can cause a catastrophic failure, so this step matters more than any other.

The easiest way to find your caliber: look at the barrel or slide of your firearm. Nearly every modern gun has the caliber stamped or engraved on it. On a handgun, check the slide (the top part that moves) or the barrel. On a rifle or shotgun, check the barrel near the receiver.

Common calibers you'll see and what they're for:

Step 2: Understand Ammo Types

Once you know your caliber, you'll notice the same caliber comes in different bullet types. The two you need to know immediately are FMJ and JHP. Everything else is secondary.

FMJ — Full Metal Jacket (Range/Practice)

A lead bullet wrapped in a copper shell. This is your everyday practice ammo. It's the cheapest option, feeds reliably in virtually every gun, and is what you should buy in bulk for range days. FMJ punches clean holes in paper and keeps going — which is why it's not ideal for self-defense (it can over-penetrate and hit something behind your target).

JHP — Jacketed Hollow Point (Self-Defense)

A bullet with a cavity in the tip that causes it to mushroom on impact. JHP is the standard for concealed carry and home defense ammunition because it expands inside the target, transferring more energy and reducing the risk of dangerous over-penetration. Quality JHP from Federal HST, Speer Gold Dot, or Hornady Critical Defense costs more ($0.55–0.80/round for 9mm vs. $0.22–0.28 for FMJ) but it's what you want in your carry gun.

For a deeper dive, read our full ammo types explained guide.

Step 3: Decode Grain Weight

"Grain" measures bullet weight — not powder charge, not quality, just how heavy the projectile is. One grain equals 1/7000th of a pound. In practical terms, grain weight affects recoil, velocity, and trajectory.

Using 9mm as an example (the most popular caliber):

The short answer for new shooters: buy 115gr FMJ for practice (it's cheapest) and 124gr or 147gr JHP for self-defense. The heavier defensive rounds generally expand more reliably at typical self-defense distances. For a detailed breakdown, see our 9mm bullet weight guide.

Step 4: Understanding +P and +P+

You'll see some ammo labeled "+P" or "+P+." This means it's loaded to higher pressure than standard ammunition, producing higher velocity and more energy.

+P is an officially recognized SAAMI (industry standards body) designation. It's safe to shoot in any modern firearm rated for +P — check your owner's manual. Most modern 9mm handguns handle +P without issue. The trade-off is increased recoil and slightly faster wear on your gun.

+P+ is not a SAAMI standard — it's a designation manufacturers use for loads that exceed even +P pressures. Only use +P+ ammo if your specific firearm manufacturer explicitly approves it.

Step 5: Your First Ammo Purchase

Here's exactly what to buy if you just purchased a 9mm handgun (the most common first gun). Adjust caliber accordingly if you bought something else.

For the range (buy first):

One box of 50 rounds of any name-brand 115gr FMJ. Winchester White Box, Federal American Eagle, Blazer Brass, or CCI Blazer are all reliable choices. This is your training ammo. Once you've confirmed it runs in your gun, buy in bulk (500 or 1,000 rounds) to save significantly on cost per round.

For self-defense (buy second):

One box of 20–25 rounds of quality JHP. The three most recommended defensive 9mm loads are Federal HST 124gr, Speer Gold Dot 124gr, and Hornady Critical Defense 115gr. Buy at least two boxes — one to carry and one to put through your gun at the range to confirm reliability. Never carry defensive ammo you haven't tested in your specific firearm.

Step 6: How Much Ammo Should You Keep?

There's no single right answer, but here's a sensible framework for new gun owners:

Minimum practical supply: 200 rounds of range ammo and 50 rounds of defensive ammo. This gives you enough for two range sessions and two loaded magazines worth of carry ammo plus spares for function testing.

Comfortable supply: 500–1,000 rounds of range ammo and 100 rounds of defensive ammo. Buying in bulk (case quantities of 500–1,000 rounds) is where you get the best per-round pricing. You'll typically save 15–30% over buying individual boxes of 50.

What about stockpiling? Ammunition prices fluctuate with political cycles, tariff changes, and supply disruptions. Buying in quantity when prices are good is smart budgeting, not hoarding. Properly stored ammo lasts decades — read our ammo storage guide for details.

Step 7: Where to Buy Ammo Online

Buying ammo online is legal in most states and almost always cheaper than buying at a local gun store. The price difference can be dramatic — $0.22/round online vs. $0.35+/round at a store for the same 9mm FMJ.

Reputable online retailers with competitive pricing and reliable shipping include SGAmmo, Lucky Gunner, Palmetto State Armory, Target Sports USA, Natchez Shooters Supplies, and Brownells. Each has different free shipping thresholds and strengths — check our deals page to compare current prices across retailers.

For a more detailed walkthrough of the online buying process, read our complete guide to buying ammo online.