Ammunition terms explained

A grain is a unit of weight. There are exactly 7,000 grains in a pound, so a 115gr bullet weighs about a quarter of an ounce and a 600gr slug weighs a little under an ounce and a half. It is an old unit that survives here because it is the one every ammunition maker in the world prints on the box.

It is the weight of the bullet only, not of the cartridge and not of the box. The brass case, the powder and the primer are not counted. This is worth knowing because the same number can be written on a box of 20 and a case of 1,000: it describes one bullet in either.

Within one cartridge, grain weight is the main thing that varies between loads. A .308 Winchester box might say 150gr, 168gr or 175gr, and all three chamber in the same rifle. Loaded with the same cartridge, a heavier bullet generally leaves the muzzle slower than a lighter one, and a lighter one faster. What each one then does over distance depends on its shape and construction as much as its weight, and it is not something a weight alone predicts.

We do not publish figures we cannot cite. Where the manufacturer states a muzzle velocity or energy for a specific load, it appears on that product page with a link to the manufacturer page it came from and the barrel length it was measured in. Where the manufacturer states nothing, we say nothing rather than estimate.

Grain also has a second, unrelated use on a reloading shelf, where it measures a charge of powder. That is not what the number on an ammunition listing means.

Every abbreviation below is one this catalogue actually uses. They describe construction: the jacket, the nose, the base. They are not grades, and a longer name is not a better one.

Two suffixes turn up attached to several of them. BT is a boat tail, a bullet whose base is tapered rather than cut flat. FB is a flat base. Both can be bolted onto almost any of the designs below, which is why the catalogue contains strings like FMJBT and TAC-TX BT.

The case is the body of the cartridge: the part the powder and primer sit in and the bullet is seated into. It is the piece left in the chamber or on the ground after the shot, and its material is a filter on this site because it changes what happens to that piece afterwards, not what happens down range. The five below are the only values our catalogue records.

The one consequence worth knowing before you order is reloading. A fired brass case can be resized, reprimed and loaded again, which is why fired brass has a resale value and why some listings advertise themselves as reloadable. Steel and aluminum cases are not put back into service that way. Nickel plated brass is brass with a plating on it, so it behaves as brass here.

The second is the range you shoot at. Some ranges do not permit steel cased ammunition, and some collect and keep fired brass as a condition of shooting there. Both are that range’s rules to make and to state, so read them rather than assuming, and a magnet settles which case you are holding: steel is drawn to one and brass, nickel plated brass and aluminum are not.

Where a listing here shows no case type at all, nobody has told us what the case is. We leave it blank rather than guess, and that product simply does not appear under any of the case type filters.

20rd means twenty cartridges in the package. Ammunition is sold in wildly different quantities, from a 5 round box of slugs to a 1,000 round case, so a price on its own tells you almost nothing: a $19 box and a $340 case are not comparable numbers until you divide.

That is why the price per round sits beside every price on this site, in the same weight. It is the price divided by the round count, and it is the figure that lets a 50 round box, a 250 round value pack and a 1,000 round case of the same load be lined up against each other. Shipping is charged per order rather than per round, so a larger package usually lands cheaper per round, but not always, and the number on the card is the one to check rather than the assumption.

Gauge is a measure of bore size, and it runs backwards from what most people expect: it is the number of solid lead balls of that bore diameter that together weigh one pound. Twelve smaller balls to the pound, twenty smaller ones still, so a larger gauge number is a smaller barrel. This catalogue carries .410 Bore, 12 Gauge, 20 Gauge and 28 Gauge. The .410 is the odd one out: it is named for its bore diameter in inches, not by the gauge system at all, which is why it is written with a decimal point.

Shell length is a safety matter, not a preference

A shell must never be longer than the chamber it is fired in. A 3 inch shell fired in a 2 3/4 inch chamber can raise pressure far beyond what the barrel is built for. The chamber length is stamped on the barrel of the gun. The length on the box is the length of the shell after it has been fired and its crimp has opened, so an unfired 3 inch shell measures under 3 inches in your hand: you cannot check this by eye or by dropping one in. Read the barrel marking and match it.

The reverse is normally fine. A shorter shell in a longer chamber is what a 2 3/4 inch shell in a 3 inch chamber is, and shotguns are built for that. Lengths in this catalogue run from 1 3/4 inch through 2 1/2, 2 3/4, 3 and 3 1/2 inch. A listing may write the same length as 2 3/4 in or 2.75 in; they are the same shell.

Why 20 gauge shells are yellow

Effectively every 20 gauge shell made is yellow, and it is not a styling choice. A 20 gauge shell dropped into a 12 gauge barrel does not fall through. It lodges in the bore ahead of the chamber, leaving room for a 12 gauge shell to be loaded behind it, and firing that second shell can burst the barrel. The industry standardised on one colour used by nobody else so that a 20 gauge shell is recognisable at a glance in a pocket, a bag or a shell holder. If you shoot both gauges, that colour is the check.

What is inside the shell

The payload is stated one of two ways, and sometimes both. An ounce figure such as 1 oz, 7/8 oz or 1 1/8 oz is the total weight of shot, or of the slug, that the shell carries. It is not the weight of the shell. A pellet count such as 9 Pellets, or 9PLT written short, is how many individual pellets are loaded, and it is normally given alongside the pellet size: 00 buck, #4 buck, #8 shot. Sizes are explained in the bullet type table above. A slug is one projectile rather than many, and its weight may be given in ounces, in grains, or in both.

Every cartridge needs a primer, a small amount of impact sensitive compound that the firing pin crushes to light the powder. There are two places to put it, and that is the whole distinction.

Centerfire puts it in a separate metal cup seated in the centre of the case head. You can see it as a circle in the middle of the base. Nearly everything in this catalogue is centerfire, and the product page names the primer type, usually Boxer, which is the type with a single central flash hole that can be punched out and replaced. That is what makes a case reloadable, and it is why some listings say so.

Rimfire spins the compound into the hollow rim around the edge of the case instead, so there is no separate primer and the base is smooth. The firing pin strikes the edge rather than the middle. A rimfire case cannot be reprimed, so rimfire ammunition is not reloadable. The rimfire cartridges here are .17 HMR, .17 WSM, .21 Sharps, .22 LR, .22 Short, .22 WMR and .22 WRF.

The two are not interchangeable in any direction, and no rimfire cartridge will chamber in a centerfire firearm or the reverse. As always, match the cartridge marked on your barrel or slide to the cartridge on the listing.

A cartridge has a published maximum pressure. +P marks a version of that cartridge loaded to a higher one, and +P+ a load above even that, which has no published standard at all. The cartridge name is otherwise the same: .38 Special +P is .38 Special, in the same chamber.

Whether a firearm is rated for +P is a statement its maker makes, in its manual, about that model. It is not something a retailer can tell you and not something we will guess at. If the manual does not say, ask the manufacturer.