Ammunition Explained: What Bullets Are Made of and How They Work

Your instructor drops a round of ammunition into your palm and you turn it over between two fingers. That's usually where the knowledge stops, and fair enough: almost none of it shows from the outside. A brass cylinder, a copper tip, everything that matters sealed inside. This guide takes a round of ammunition apart properly, from what the four parts are made of, to what happens in the millisecond after the firing pin drops, to why a few square millimetres of exposed lead decide what an underground range will stock. One thing first, because it makes the rest easier. A bullet is not the thing you load. The bullet is only the projectile at the front. The whole item is a cartridge.

TL;DR: Four parts make a cartridge: brass case, primer, propellant powder, bullet. Pull the trigger and a chain reaction runs through all four in milliseconds, throwing off gas at roughly 3,100°C. The bullet is a lead core in a copper jacket, and how that jacket goes on is what separates the two rounds on our shelf. Every shooting package sets out which weapons you fire and how many rounds you get with each, and every round is loaded and fired on your instructor's command.

What a Cartridge Is Made Of

Four parts, and none of them optional.

• The case: the container holding the rest together. Usually brass, sometimes nickel or steel. The bit that pings off the concrete beside you.
• The primer: a small cup in the base, holding an impact-sensitive compound seated over a tiny anvil. The ignition switch for the whole system.
• The powder: modern propellant, nitrocellulose based, sometimes with nitroglycerin in the mix. It does not detonate. It burns, very fast, and that distinction is the entire basis of how a firearm works.
• The bullet: the projectile seated in the case mouth (lead core, copper jacket, usually). The only part that leaves the barrel.

So here's a pedantry worth having. Say you fired fifty bullets; you actually fired fifty cartridges. Fifty bullets went downrange. Fifty empty cases hit the floor. Latvian, as it happens, gets this right where English doesn't: our shop labels the product patrona, the Latvian word for cartridge, not lode, which is the bullet on its own.

How a Cartridge Actually Works

The whole sequence, from firing pin to bullet leaving the barrel, is measured in milliseconds. Slow it down and it runs like this.

The firing pin hits the primer cup and deforms it, crushing the priming compound against the anvil underneath. That compound explodes. Hot gas shoots through a small flash hole into the case, lights the propellant, and the powder burns off expanding gas at a temperature of roughly 3,100°C.

Now the part almost nobody knows about. That pressure doesn't only shove the bullet forward; it also irons the walls of the brass case outward, pressing them hard against the chamber, and that seal is what stops hot gas escaping backwards towards you. Cheap disposable brass, doing gasket work. It forms itself at the exact moment it's needed, then gets binned.

Only once the pressure is high enough does the bullet break the grip of the case mouth. It accelerates down the barrel with gas chasing it, and exits. The case, expanded and empty, gets ejected. Next round feeds in behind it.

Every round of ammunition on the shelf runs that same four-step sequence. That's the whole working principle. A controlled, extremely fast burn in a sealed steel space, with one deliberately weak point: the bullet.

What the Bullet Itself Is Made Of

Every cloud has a silver lining. Every bullet has a copper one. Nearly all of what you'll fire here is two materials: a lead core for weight and density, and a copper jacket wrapped round it. Lead on its own is soft, and fired bare it smears fouling down the inside of a barrel. The jacket fixes that.

The interesting bit is how the jacket goes on. Two methods, two different bullets.

• Full metal jacket (FMJ): the jacket gets pressed on mechanically, and that process leaves the lead core exposed at the base, the end facing the burning powder.
• Total metal jacket (TFMJ): the jacket is electroplated on, so copper deposits across the entire surface. Base included. No lead exposed anywhere.

From the outside you'd never tell them apart. The difference is a few square millimetres of lead at the bottom of the bullet, facing away from you, and it's why the two rounds on our shelf are priced twenty cents apart.

The Ammunition We Stock at GunRange.lv

Everything in our ammunition category is 9×19mm, also written 9mm Luger. It's one of the most widely used pistol cartridges in the world, and the one you meet first.

Read one line of that table and every ammunition box in the world becomes readable. Three things on a label carry the meaning.

• The calibre (9×19mm): the dimensions of the cartridge, which decide what it fits. A round of the wrong calibre doesn't go in a bit tighter. It won't chamber at all.
• The bullet type (FMJ, TFMJ): how the jacket was applied, covered above.
• The weight (124 gr): grains, a unit of bullet mass, not grams. 124 grains is roughly 8 grams and one of the commonest weights in 9mm. Heavier bullets feel like a push, lighter ones snap.

You buy these in our shop at the range, over the counter. You'll hear both words on the firing line; ammo is just the short form. Our online store stocks optics and gear, while the range ammunition stays here.

Why the Base of a Bullet Matters Underground

This is where a few square millimetres of exposed lead stop being trivia.

The US National Institute for Occupational Safety and Health has studied indoor ranges directly, and found that switching to fully jacketed and coated ammunition reduced airborne lead concentrations by 94 to 97 per cent. The same research is equally clear that ventilation, cleaning, and basic hygiene do the rest of the work.

To be straight about it: that research measured law-enforcement trainees running high-volume courses day after day, not a visitor firing thirty rounds on a Saturday. What it does explain is why a range operator pays attention to which ammunition it stocks and to the base of a bullet, and why a sealed bunker gets a ventilation strategy before it gets guns. Sellier & Bellot describe their Nontox round as ekoloģiski tīra, environmentally clean. That's the entire idea, and it's why we stock it.

Rimfire and Centrefire: Where the Primer Lives

Ammunition divides one more way, and it comes back to that primer.

• Centrefire: the primer sits in its own cup, dead centre in the base of the case, exactly as described above. Everything in 9×19mm is centrefire. More powerful, more reliable, and you can reload the case.
• Rimfire: no separate primer at all. The priming compound is spun into the rim of the case itself, and the firing pin strikes the edge instead of the middle. Cheaper, much softer recoil, quieter, single use.

We run both. The CZ 512 Tactical and the ISSC MK22 on our arsenal wall are .22LR, which is rimfire, and it's the gentlest thing we hand anybody. Nobody starts out as James Bond. If you've never fired a gun in your life, that's a genuinely pleasant place to begin, and nobody here will think less of you for it.

Conclusion

Ammunition looks sealed off and technical, and it comes apart in four sentences. Four parts. A fast burn in a sealed space. A brass case that seals itself, does one job, and gets binned. One deliberately weak point, and that's the piece that leaves the barrel.

Whatever ends up in your hand here, a rimfire rifle or a centrefire pistol, it was chosen for a building that has been underground since the Cold War, and and handled under the command of somebody who has done it a great many times before. Turn up knowing none of this and you'll still shoot well. Knowing it just means the round in your palm stops being a mystery object.

Book a shooting package at GunRange.lv and find out what 124 grains actually feels like!

Four parts go in. One comes out the far end.