(2450 words)

When you choose a firearm, you choose it for a reason. Yes, I have some firearms that are in the safe because they followed me home. But there are many more that were picked for a reason.

We pick our firearms for looks, for the feel in the hand, the cool factor, the weight, and a multitude of different options.

We also pick for practical reasons. As an example, I have critters that get into the chicken house and into the feed and are sometimes on the porch. There are bears that roam the area. These are all targets at different times.

There is a display rack in the living room. It holds four lever action rifles. The blue haired fairie has them named, “bear”, “deer”, “raccoon”, and “squirrel”. In order, 45-70, 30-30 Winchester, .357 Magnum, .22 LR. Each has a different purpose, coming from different requirements.

Anybody who is anybody will tell you that those rifles really don’t have the ability to go the distance. They are all 100 yards, or less, rifles. The real truth is that I can ring steel at 100 yards with any of them. But getting a line of sight of 100 yards around here is difficult.

In the safe is a Remington 700 in 7.62×51. I’ve taken deer with it at around 600 yards. That rifle has great optics on it, and it was designed for taking shoots at that distance, or greater.

When looking at a firearm, we can look at subjective items, we can also look at the objective parts. The Mauser has a small notch for a rear sight and a thin blade for the front sight. I have difficulty picking up the sights. That is an objective evaluation.

The Enfield has sights that are easier for me to pick up and use. The Garand has great sights.

These are objective factors.

There are other objective factors, such as overall weight, accuracy, cartridge/caliber, magazine compatibility, parts and ammunition availability. These all make a difference.

We choose our ammunition for both subjective and objective reasons.

Measurements

We can measure different factors of bullet performance. One of the first is velocity.

Today we use a chronograph. This device can sense the shadow of a bullet passing over the two sensors. By knowing the distance between the two sensors and the time between detecting the bullet, we can calculate the velocity of the bullet as it flies over the chronograph.

Before we had electronic chronographs, we had mechanical chronographs. One of the methods used two spinning disks. The disks were attached to an axel rotating at a known speed. A round was then fired into the spinning disks. That bullet would pass through the first disk and then through the second disk.

My measuring the angle difference between the bullet holes, we know how much the disks rotated while the bullet flew from the first disk to the second disk. That angle, combined with the speed of rotation, gives us the time it takes for the bullet to travel the distance between the two disks.

Once we know that time, we can calculate the velocity.

We can also measure the weight of the projectile. That is an objective measurement.

Another measurement is the size of groups at a known distance and the ability to hit a target at a distance.

All of these things are objective measurements.

There is another objective measurement that can be of interest, how well does the bullet with a given velocity penetrates a given target.

Years ago, I bought my first “steel target”. I set it up at 100 yards and shot at it with 5.56×45, 7.62×51, and something else.

I thought I was hitting the target but nothing was happening, with the 7.62×51. Switching to 5.56, I still could not observe hits.

I walked the walk of shame to the target to see what had happened. What I found was that 7.62 makes 8 mm holes in steel and 5.56 makes 6 mm holes.

Since then, I’ve learned much more about steel and would never imagine that a piece of 1/8″ A-36 steel would stop any rifle round. When I purchased my real steel, it was AR-500 and 1/2 thick.

So we can measure penetration in a known steel. That does not include A-36 or 1018.

We can also measure penetration in other targets. Paul Harrell uses what he calls a “Meat Target”. This is a target made of layers, front to back, t-shirt, faux leather, pig ribs, oranges, pig ribs, faux leather, another t-shirt.

The t-shirt is the expected clothing. Sometimes more, sometimes less clothing is used. The faux leather represents skin tissue. The pig ribs simulate our ribs, the oranges represent our longs, and then we repeat on the way out.

The problem with this type of target is that we might not get consistent results. Does it mean anything if we hit a rib vs. miss all the ribs? Are the ribs the same thickness? Are those oranges the yucky ones with 1/4+ of peel on them, or the thin-skinned tasty ones?

We used to use 1-inch thick oak planks for penetration testing. The number of planks the bullet went through was a measurement of how good the penetration was.

Today, we use ballistic gelatin. The gelatin must be calibrated to compare different tests. The calibration method is to shoot a round, steel ball into the block of gelatin at a given velocity. The penetration should be 3 inches to match other calibrated gelatin.

There is also a temperature requirement.

Once you have the gelatin, you can shoot your round into it. You can examine the depth of penetration and the wound cavities to have an idea of how the round performed.

Here is the important thing though, sometimes the results are not meaningful. It is possible to create a bullet that will do well in gelatin, but which performs much worse in practice.

This is always a problem when people are manufacturing to a goal that is not a full representation of the actual requirements.

In an example from photography, I was asked to provide some images that were 2 inches by 3 inches. This took me just a few seconds. It took that little because the request was meaningless. Images are measured in pixels. We convert them to inches by setting a resolution of pixels per inch. If I had an image that was 100 by 150 pixels, I can make it a “2×3 inch” image by seeing the DPI to 50.

That image is far too small. On the other hand, I could submit the image as 3328 by 4992 with the resolution set to 1664 DPI, and it would still be “2×3 inches”.

45 ACP

The US Army issued Single Action Army revolvers for a time. In the late 1800s, the U.S. Cavalry started to replace the SAA with modern revolvers in .45 Colt. The power was nearly the same.

Both were black powder and both used bullets around .44 inches. The .45 Colt was a cylinder with a rounded nose. The SAA could shoot a conical or round ball.

The Army, deciding to be different, went with .38 Long Colt.

Then they had to actually use these weapons. What the found was that the .38 Long Colt didn’t have the “stopping power” that was needed. The same was true of other calibers and firearms. They lacked that magic “stopping power”.

This led to extensive testing in 1904. What came of that was a requirement for a round of at least .45 caliber.

The testing done before adopting the .38 Long Colt was not good enough. What they measured did not result in an ability to judge “stopping power”.

Accuracy

There are people who have little difficulty putting rounds on target out to 1000 yards, or more. There is a science to being able to shoot that far accurately. There is also an equipment requirement.

Assuming that we have a mechanical hold on a rifle and that we can aim it, when we press the trigger remotely, we should get repeatable results.

To get repeatable results, we have to have consistent cartridges. The bullet must leave the barrel with the same velocity, every time. If the velocity is inconsistent, the accuracy will suffer.

Ignoring barrel changes and fouling shoots, just focusing on the bullet and cartridge.

To get that consistent velocity, the bullet shape and weight must be consistent. The charge must be consistent, the ignition must be consistent. The release from the case must be consistent. The distance before engaging the rifling must be consistent.

And those things must be matched as a whole to get the best results.

When I am reloading, I crimp my cartridges. I do not do long-range shooting. More of the shooting I do is from stuff that is knocked around. While having a soft crimp on my 30-06 might give me better accuracy, it is more important to me, that the bullet does not change its seating depth or fall out.

To get the accuracy, I want out of my reloads, I am careful with case prep, charge weights, bullet weights, bullet shape, seating depth and then have a consistent, but not light, crimp. That is the balance I choose.

Because of the die I use to crimp the bullet to the case, that is the place of least consistency. Case length in 5.56×45 ranges from 1.750 to 1.760 inches. If the case is longer than 1.760 inches, it is trimmed to 1.750 inches.

This means that the cases that I am reloading are of different lengths. Since the crimp strength is based on the case length, the amount of crimp also varies.

So our first measurement of accuracy is group size. The smaller the group size, the more accurate the firearm/cartridge system.

Some bullets fly better than others. Those that fly better generally have less drag and thus maintain their velocity longer.

The more “drag” the faster the bullet looses speed and the more likely it is to have flight dynamics issues. I.e., it turns as it flies, causing it to veer off course.

Ballistic Coefficient

Another measurement we have is the Ballistic Coefficient of a bullet. This is a single number which represents how much drag a bullet has at different velocities. There is a G1 and a G7 table.

The closer to 1.0 the Ballistic Coefficient is, the more aerodynamic the bullet is. The better the Ballistic Coefficient is, the longer the bullet will retain its velocity.

The Ballistic Coefficient of a bullet is not so much calculated as observed. By observing the velocity of the bullet at different distances from the muzzle, we can determine the B.C. To say it differently, B.C. are determined experimentally.

Some manufacturers of bullets will publish the B.C. of their bullets.

Here are a few B.C.s

• Federal Champion Training, 22 LR 36 grain: 0.125
• CCI Sub-Sonic HP 22 LR 40 Grain: 0.120
• Hornady SST bullets: 30 Cal .308 150gr 0.415
• Hornady Varmint 22 cal .224 55grain: 0.235
• Hornady ELD-Vt: 22 cal .224 62gr 0.395

Different bullets have different flight characteristics.

I use the CCI Sub-Sonic for taking squirrels. It is quieter. If I had a can on the rifle, it would be quieter still. The downside of that is that I have greater bullet drop. About 0.5 inches per 30 ft of drop.

Ballistic Gelatin

Remember how we figured out the B.C. from observation? Ballistic Gelatin is the same. It is meaningful only through experimental data.

Back in 1986, there was a shootout between the FBI and William Matix and Lee Platt. At the end of the shootout, Matix and Platt were both dead, but they had killed two FBI agents and wounded five others.

During the shootout, both Matix and Plat were shot multiple times, yet they were able to continue to return fire.

There were many rounds exchanged, many people wounded, yet they kept fighting.

This shootout led the FBI to start their own terminal ballistics study. They turned to ballistic gelatin as their medium of choice. The gelatin has similar characteristics to pig muscle. Which is a polite way of saying human muscle tissue.

The formula is 1 part 250 bloom type A gelatin to 9 parts of warm water, by weight.

Just before it is used, a calibration shot is fired. This is a .177 caliber steel BB from an air rifle. The gelatin is calibrated when a BB at 600 ft/s pen rates between 3.4 and 3.7 inches.

You can learn more from —Duncan MacPherson, Bullet penetration: modeling the dynamics and the incapacitation resulting from wound trauma (Ballistic Publications 1994).

The FBI gathered information from incidents where shots were fired and a target stopped. From this, they acquired matching ammunition and fired into the calibrated ballistic gelatin.

What they discovered was that rounds that were successful at stopping threats penetrated to 12-18 inches.

Does this mean that a round that penetrates 18 inches of gelatin will penetrate the same distance in a human? No! Absolutely not.

We are not gelatin. We are made up of layers of different stuff. A bullet traveling through me will pick up a heavy coating of lubricant (grease/fat) as it passes through. On the other hand, going through my swim team son, there just isn’t that much fat.

Man, that was impressive!

I took a trash panda with a 30-30 Winchester with a cast lead bullet. It was a headshot. The head came apart. There was blood and brains everywhere. The bullet continued on and into the ground. That was “impressive” but in an overkill way.

I harvest squirrels with .22lr sub-sonic rounds. There is nothing “impressive” about it. But a single, well-placed shot, and they are dead before they hit the ground. Headshots.

5.56×45 55gr FMJ into a pumpkin? Boring.

5.56×45 55gr Varmint SP into a pumpkin? Impress shower of pumpkin guts.

.303 British FMJ into large pumpkin? Not much. .303 British with SST on top? Pumpkin parts. Soda bottles ruptured.

5.56×45 55gr over 22.1 gr of IMR 4895 with #41 primers at 100 yards? Nice groups. Quietly impressive.

Conclusion

Figure out what you want to know about the rounds you load.

The cheapest is accuracy testings. Do they group tightly? Do they group as tight as commercial ammunition, or do they do better, or do they do worse?

Figuring out the velocity isn’t that expensive. A chronograph can be had for under $100. It can tell you the velocity of every round you send down range over it. This will tell you the consistency of your loads, and it will give you that starting number for the ballistic calculations.

You can make your own targets for penetration testing. How many 2 litter bottles does it go through? How many water jugs? Maybe you make up your own gelatin and test with it.

Regardless, there is more to know about bullets and bullet performance than I touched on here.

Many thanks to the commentors that said things like “You should mention…”