Ammunition Q&A – by Rob Taylor

Since the Covid lockdowns and the current financial crisis lots of people who previously didn’t own guns are buying them and finding themselves needing to learn a whole new language – namely what all those little abbreviations and other writings on boxes of ammunition mean. This is by no means an exhaustive list but simply a number of questions I’ve heard and answered over time.

What’s a Jacketed Bullet? A blog called Aiming Expert puts it this way:

Jacketed ammunition refers to ammunition that has an extra cover (jacket) on the lead core.

This jacket can be made from copper, copper alloys, aluminum, or steel. Nowadays, most of the ammunition has a steel jacket since it’s cheaper.

The use of metal jackets became mandatory during the transition from black powder to smokeless powder. Initially, the black powder had modest velocities and temperatures which lead could handle. 

Higher velocity black powder cartridges were later developed, making it necessary to use metal jackets. On the other hand, Smokeless powder has very high velocities and temperatures, which can melt the lead core. 

That’s why most of the cartridges with smokeless powder are jacketed.

There were also international treaties that required the military not to use expanding bullets. So the metal jackets were designed to minimize the expansion of the bullets, prevent their deformation, and even reduce fouling. 

Metal jackets are designed with different thicknesses and hardness to suit various ballistic performances.

The most common term associated with jacketed ammunition is the Full Metal Jacket (FMJ). FMJ applies if the jacket covers the lead core completely. If it doesn’t, it’s referred to as semi-jacketed. 

Jacketed Hollow Points (JHP) is another example of jacketed ammunition.

FMJ ammunition is usually considered training ammo but you’ll find it in lots of dead people. It makes cleaning your gun easier. My favorite .32 S&W Long cartridge is a Fiocchi 97gr FMJ. In older handgun cartridges, particularly revolver cartridges, it’s common to find exposed lead bullets in ammo. In rifles not so much. Shotgun slugs are still usually just a giant slug of lead unless you get specialty ammo.

Some semi-autos are designed around using FMJ ammunition. The 1911 is particularly notorious for jamming among some shooters but experienced 1911 owners will tell you that many of the guns simply “prefer” FMJ – something about how the magazine feeds. Newer quality 1911s usually don’t have a problem but replicas of the originals or your grandfather’s old gun might like FMJ.

FMJ also penetrates more than other rounds because the lead doesn’t expand. Lead is soft so even rounds that aren’t Hollow Points (We’ll get to that) will “mushroom” when hitting things, flattening out and deforming in such a way that it’s slowed down. This is good because it means more of the kinetic energy is dumped into the object. FMJs don’t expand, they just keep on trucking until they run out of energy. This is considered a bad thing by many because it means the round is more likely to punch through an assailant and into another person.

What’s a Hollow Point? Like the name says it’s a bullet where the point has been hollowed out to create a cavity that creates expansion when the bullet enters tissue. Here’s a demonstration using Super Vel brand Solid Copper Hollow points of different calibers fired into ballistic gel to show you the point of the design:

The gelatin here is supposed to mimic human tissue (sans bones of course) so you see that while an non hollow point bullet will basically make a hole the size of the bullet in a person, hollow points create cavernous wounds thus being more effective in self defense and more humane in hunting.

What is +P and +P+? I stay away from that sort of ammo for many reasons but I’ll let The Truth About Guns Summarize:

When a gun goes off, the powder inside the cartridge burns and creates super-hot expanding gasses. Those gasses eventually push the bullet down the barrel, as that’s the path of least resistance for the gasses to escape. But since multiple manufacturers make ammunition marked with the same caliber designation, there needed to be a way to standardize the characteristics of each caliber so that gun makers and ammo makers could make products that work perfectly together and won’t blow up.

The good people at SAAMI (the Sporting Arms and Ammunition Manufacturers’ Institute) publish the official specifications for every cartridge. They dictate everything from the dimensions of the cartridge to the maximum pressure that the cartridge should produce. That keeps everyone on the same page when they make guns and ammo.

That second part, the maximum pressure bit, is extremely important. Gun makers use that number to figure out how thick the gun’s chamber and barrel should be to safely contain that pressure round after round. The guns are tested with a high pressure “proof load,” which is designed to produce a much, much higher pressure in the barrel than the listed maximum chamber pressure according to SAAMI.

The proof load replicates the “worst case scenario” and ensures that the gun can safely contain such a round and still operate, but guns are designed to function mainly on the lower standard pressure rounds. The gun will work using proof loads, but the parts will wear out extremely fast and the gun will quickly become unusable and unsafe.

[…]

While standard pressure ammunition is nice, some people (especially those using it in self defense firearms) believed that they needed more power. …

So that’s the impetus behind the +P and +P+ stuff, people wanting to get more velocity or a heavier bullet in a traditional and standardized cartridge than the specs would allow without changing the dimensions. Unfortunately, the result of those changes is that the chamber pressure of the rounds exceed the maximum pressure specifications for normal, factory ammunition.

+P, pronounced “plus pee,” is a recognized “overpressure” load for ammunition that SAAMI officially blesses. The institute publishes the maximum allowable pressures for these loads as well as the standard cartridges, allowing firearms manufacturers to produce guns capable of safely handling round after round of the hot stuff without damaging the gun. +P loadings are offered for the standard self defense rounds of 9mm Luger, .45 ACP and .38 Special among others.

Since +P cartridges are typically only 10% above the normal pressure of a cartridge they will work in any properly maintained gun (the proof round is still a much higher pressure), but they will wear it out sooner and increase the chances that the gun will suffer a “structural failure.” Which is code for “blow up in your hand.” So the common advice is to not use +P as range / practice ammo.

+P+ or “plus pee plus,” is a loading above the already over-loaded +P designation. This is for people who don’t think that +P is enough “stopping power” and want even more. But this is the point at which SAAMI draws the line. There are no standards for +P+ ammunition, it is simply “more” than +P.

Emphasis mine. The one exception to this is a round not popular in the United States but common in Central America called the .38 Super. This round was invented in the 1920s for 1911s as a better preforming upgrade to a round called the .38 ACP. The Super was designed to penetrate car doors of the time period. It became popular (and is still popular) with competitive shooters. In the early 1970s manufacturers started putting +p on the boxes to differentiated it from the earlier .38 ACP because the Supers can be chambered in guns designed for the earlier .38 ACP which is dangerous. but .38 Super isn’t an over pressured round and if you have one don’t worry about it.

Personally I think that if you want more power you just go up a caliber. While +P is technically safe, it still wears out the gun faster.

What’s Soft Point? SP or JSP (Jacketed soft point) are FMJs with the tip made being exposed lead. It’ll look like this:

or in rifles this:

They are a compromise round that gives you (slower) expansion like a hollow points but also the benefits of FMJ of being easer to clean up after. They’re also cheaper in some cases than marketed self defense ammo.

What’s SWC mean? Semi Wad Cutter. Wad cutters are a type of target ammo that is essentially a flat cylinder of lead designed to cut a neat, visible hole in a paper target. This is what a Fiocchi wad cutter in .38 Special looks like:

Old timers back in the revolver days thought wad cutters would make great self defense rounds because they’d punch a whole in a attacker that couldn’t be closed. Since all bullets are potentially fatal no one can talk people who think that out of thinking that because you’ll never be able to prove wadcutters aren’t capable of killing folk. But people can and did improve the wad cutter design for self defense by making it a semi wad cutter which has the blunt flat tip of a wadcutter on the “shoulders’ of a more traditional design. They’re popular with people who conceal carry .38s.

What should I carry? That depends on the gun and your situation. I like Semi wadcutter hollow points (SWHP) but it’s rare to see those outside big bore revolvers. For semi-autos I prefer whatever ammo that particular gun runs the best on.

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