Since there are probably many folks new to firearms in the recent months, it may help to convey a sense of awe and respect for the power which they possess. I intend to use practical examples to give the average person a relative understanding of firearm ballistics; dealing primarily in the overall energy they are capable of unleashing at varying ranges.
I will focus on the three most common military-spec cartridge calibers found in semi-automatic battle rifles in the U.S.: 7.62x51mm NATO (.308 Win), 7.62x39mm Soviet/Russian and 5.56x45mm NATO (.223 Rem). I will also address some comparisons with handgun ammunition and even the .30 Carbine round.
Note: This article make fair use quotes and cites data from a variety of references. See the References list at the end of the article for links. The author thanks the writers of these fine references for their many hours of research.
It is my hope that people who read this will not only further their knowledge about firearms, but find that it may aid them in their quest for wisdom when it comes to knowing the limitations of their weapons.
The statistics used herein are averaged and aggregated from various sources, primarily focusing on military-spec ammunition (what most civilians wind up buying as “military surplus” ammunition from various nations). Since most NATO nations comply with similar cartridge standards, comparing their attributes is easy.
When it comes to the 7.62x39mm Soviet cartridge, I averaged Tula, Vympel and Barnaul munitions factories from Russia, since Russia is the home where the 7.62x39mm cartridge was born and standardized. While most of us know these brands by their commercial names: Wolf Military Classic, Golden Tiger and Brown Bear, the ammunition itself is made to Russian military specifications.
.30 Caliber Carbine (aka US .30 Carbine) is added to the analysis of modern military cartridges to give those people who use it a realistic idea of its limitations. Not to detract from the merits of a compact, lightweight, easy-to-carry carbine or its light ammunition, but to compare it apples-to-apples when it comes to net power.
All rifle cartridges used in these statistics were Full-Metal Jacket (FMJ–meaning the entire lead bullet is encased in a cupronickel metal covering). The .30 Carbine ammunition statistics can be applied to either FMJ or JSP because both projectile types are the same mass, with the same velocity and with almost identical sectional density.
As we all know, mass x velocity = energy. But it’s not so simple. Let’s visit some popular mathematic formulas:
F = ma
Force equals mass times acceleration.P = Fv
Power equals force times the constant velocity.KE = 1/2m v2
Kinetic energy equals one half of mass times velocity squared.
So a bullet’s speed (velocity) means nothing to us unless we know its mass. Coupled together we get:
Caliber, Bullet Weight, Muzzle Energy and Muzzle Velocity
7.62x51mm NATO 147 grain (gr)~2,550 ft/lbs (3,457 joules) @ 2,700 fps (FMJ)
7.62x39mm Soviet 123 gr ~1,525 ft/lbs (2,067 joules) @ 2,360 fps (FMJ)
5.56x45mm NATO 62 gr ~1,250 ft/lbs (1,694 joules) @ 3,050 fps (FMJ)
.30 Caliber Carbine 110gr ~965 ft/lbs (1,308 joules) @ 1,995 fps (FMJ and JSP)
.45 ACP 230 gr ~390 ft/lbs (528 joules) @ 875 fps (JHP)
9x19mm Luger/Parabellum 115 gr ~385 ft/lbs (521 joules) @ 1,225 fps (JHP)
The .45 ACP (Automatic Colt Pistol) and 9x19mm pistol cartridges were added as a comparison for those familiar with handguns and their energy at point-blank range. At 50 yards, both standard .45 ACP and 9x19mm defense loads are roughly equal in net energy (~350 ft/lbs or 475 joules each).
When measuring both energy and velocity at the “muzzle” of a firearm, it is basically “point-blank range” which when describing firearms [versus artillery] means within a few yards of the muzzle.
Now these figures are measured within a few feet of the muzzle (hence the term “muzzle energy” or “muzzle velocity”), which is the most powerful the projectiles will be throughout their ballistic path. Because of wind resistance, they will decelerate (and thus lose energy) at varying distances. This is why we get the term “effective range,” as beyond a certain point the energy is too low to be expected to be nominally effective. Also, keep in mind some projectiles will drop rapidly as their ballistic arc terminates (and is pulled down by gravity). The energy and velocity at ranges listed below are assuming the shooter is holding the sights high enough to get the projectile there before it hits the ground…at a certain point this practice becomes futile and borders on indirect fire, going back to the concept of “effective range.”
Remember; so long as the air resistance remains constant, so too will the rate of deceleration of the projectile.
Also, bear in mind that while some bullets travel slower than others, if they are heavier they can have a net force which is more than the other (e.g. 7.62×39 has a muzzle velocity (MV) of 2,360 fps and the 5.56 NATO has a MV of 3,050. While the 5.56 NATO is roughly 700 fps faster at the muzzle than the 7.62×39 projectile, the 7.62×39 is almost exactly twice the mass of the 5.56 NATO).
The statistics shown here of muzzle velocity and energy are all given through 20″ rifle barrels (though not certain on the .30 Carbine figures, though since there is primarily only one common firearm which fires the cartridge, the M1 Carbine which has an 18″ barrel, it is assumed all statistics for that cartridge are applied for a 18″ barrel). The shorter a rifle barrel is, the less time the expanding gasses from the compressed burning powder have to accelerate the projectile before it exits the barrel (which ends acceleration and begins deceleration due to air resistance). A 20″ barreled AR-15 will generate faster projectile velocity and higher net bullet energy (using identical ammunition) than a 16″ barreled AR-15 Carbine [such as an M4gery or a typical civilian CAR-15].
To compare accordingly, an AK rifle and a civilian AR-15 carbine both have 16.25″ barrels and thus would have roughly the same ratio of velocity and energy (though at lower values). If one wanted to compare 20″ to 20″ inch, maybe a standard length AR-15 and a Russian SKS (or even Romanian RPK) would be a fair comparison (either may be slightly over 20″ but would be a closer comparison than a full-length AR-15 to a 16″ bbl AK).
Probably the fairest means of comparison using statistics below is to assume the cartridges were fired from the following 20″ barreled rifles:
7.62x51mm NATO : FN-FAL (most have 21″ barrels but many can be found with ~20″ barrels)
7.62x39mm Soviet : SKS (most have ~20″ barrels)
5.56x45mm NATO : AR-15 (standard size has ~20″ barrel)
The measure of mass used for firearm projectiles (bullets) is grains. A grain is a unit of lead mass measurement, roughly equal to 1/3 of a carat or 65mg. 16 grains is roughly equal to 1 gram. Note that grains in bullet mass differ from from ” grains” of smokeless powder (nitro-cellulose) propellant, which is not used in this article.
A hard baseball is about 5-1/8 ounces or 149 grams. This equates to 2,300 grains in mass.
The energy being used is in foot-pounds of force and in joules. The best way to describe a single foot-pound of force, “is the amount of energy expended when a force of one pound acts through a distance of 1 foot along the direction of the force.” While not scientifically “correct,” the terms “force” and “energy” are used interchangeably in this article.
Also, keep in mind that if a bullet does not release all of its energy into a single target, it will go through it while retaining the remainder of its force while coming out the other side. This is why most modern handgun projectiles are Jacketed-Hollow Points (JHPs), so they mushroom in deformation to a larger diameter (usually ~0.72″ regardless of what caliber it started out as), thus increasing surface area and resistance in the target medium and will then release more energy over shorter distance (basically to prevent over-penetration at close range). Over penetration of a target means that not all of the kinetic energy in the projectile winds up being released in that target. From the target’s perspective, that means less overall damage.
Rifle cartridges are also designed to deposit as much energy as possible in a target in a relatively short distance. The 5.56mm NATO projectile, if within 200 yards, will often critically destabilize while acutely decelerating in a soft target medium and fragment into many pieces; releasing its energy all at once in a very small distance. The 7.62x39mm Soviet will usually tumble a few times (yaw/pitch) in a soft target medium and in doing so release a spike of its remaining energy in each tumble (and if it stops in the medium, will wind up facing backwards). The 7.62mm NATO projectile will usually tumble once and if it does not exit the other side of the target medium (which it usually does at closer ranges), it will expend all of its energy into the target and end up facing backwards–this is due to the projectile’s point of balance being closer to the rear, as the back half of most rifle projectiles are heavier than the front. Once any of the Big Three cartridge projectiles begin rapid deceleration in a target medium, their centrifugal spin-stabilization (caused by the rifling in the rifle barrel–similar to a nicely thrown “spiral” pass of an American football) usually fails and the laws of physics continue with inertia, resistance, velocity and mass in the target medium.
Now, let’s get into the meat and potatoes of mass, velocity and energy:
A 90 mph (132 feet per second, or fps) fastball (major league baseball is 149 grams, 1/3 of a pound or 2,300 grains) exerts approximately 60 ft/lbs of force as the pitcher releases it:
Baseball (Fastball) 2,300 grains ~60 ft/lbs (81 joules) @ 132 fps (90mph)
This may not be really easy to envision in any practical sense of energy when thinking of foot-pounds of force, so joules are also included.
1 joule of energy is equal to the force required for an average adult human to pick up an apple from the ground to their waist (~1m). Conversely, 1 joule is the amount of force released when that same human drops that same apple from that height. Since an apple weighs about the same as a baseball, a person must exert 81 times the force needed to pick up an apple to pitch a 90mph fastball.
Now that a few rough practical examples of applied force have been given, let us now examine the Big Three military-surplus cartridge calibers’ energy at varying distances (.30 Caliber Carbine and two pistol calibers are thrown in as a comparison to more modern military cartridges):
Caliber, Bullet Weight, Muzzle Energy and Muzzle Velocity
7.62x51mm NATO 147 gr ~2,550 ft/lbs (3,457 joules) @ 2,700 fps (FMJ)
7.62x39mm Soviet 123 gr ~1,525 ft/lbs (2,067 joules) @ 2,360 fps (FMJ)
5.56x45mm NATO 62 gr ~1,250 ft/lbs (1,694 joules) @ 3,050 fps (FMJ)
.30 Caliber Carbine 110 gr ~965 ft/lbs (1,308 joules) @ 1,995 fps (FMJ and JSP)
.45 ACP 230 gr ~390 ft/lbs (528 joules) @ 875 fps (JHP)
9x19mm Luger/Parabellum 115 gr ~385 ft/lbs (521 joules) @ 1,225 fps (JHP)
Energy at 100 yards
7.62x51mm NATO ~2,100 ft/lbs (2,847 joules) @ 2,550 fps
7.62x39mm Soviet ~1,200 ft/lbs (1,626 joules) @ 2,104 fps
5.56x45mm NATO ~970 ft/lbs (1,315 joules) @ 2,650 fps
.30 Caliber Carbine ~600 ft/lbs (813 joules) @ 1,570 fps
Energy at 200 yards
7.62x51mm NATO ~1,750 ft/lbs (2,374 joules) @ 2,331 fps (now moving faster than 62 gr 5.56NATO)
7.62x39mm Soviet ~915 ft/lbs (1,240 joules) @ 1,825 fps
5.56x45mm NATO ~735 ft/lbs (995 joules) @ 2,310 fps
.30 Caliber Carbine ~375 ft/lbs (508 joules) @ 1,240 fps (equal in force to 230 gr .45ACP @ ~10 yards)
Energy at 300 yards
7.62x51mm NATO ~1,450 ft/lbs (1,965 joules) @ 2,125 fps
7.62x39mm Soviet ~690 ft/lbs (935 joules) @ 1,585 fps
5.56x45mm NATO ~550 ft/lbs (745 joules) @ 2,000 fps
.30 Caliber Carbine ~265 ft/lbs (359 joules) @ 1,040 fps
Energy at 400 yards
7.62x51mm NATO ~1,200 ft/lbs (1,625 joules) @ 1,931 fps (equal in force to 5.56NATO @ ~15 yards)
7.62x39mm Soviet ~515 ft/lbs (700 joules) @ 1,370 fps
5.56x45mm NATO ~405 ft/lbs (550 joules) @ 1,718 fps
.30 Caliber Carbine ~210 ft/lbs (284 joules) @ 930 fps
Energy at 500 yards
7.62x51mm NATO ~1,000 ft/lbs (1,355 joules) @ 1,750 fps
7.62x39mm Soviet ~395 ft/lbs (535 joules) @ 1,200 fps (equal in force to 230gr .45ACP @ ~2 yards)
5.56x45mm NATO ~290 ft/lbs (393 joules) @ 1,460 fps
.30 Caliber Carbine ~175 ft/lbs (237 joules) @ 850 fps
Energy at 600 yards
7.62x51mm NATO ~810 ft/lbs (1,100 joules) @ 1,560 fps (equal in force to 5.56NATO @ ~150 yards)
7.62x39mm Soviet ~280 ft/lbs (379 joules) @ 1,030 fps
5.56x45mm NATO ~172 ft/lbs (233 joules) @ 1,122 fps
.30 Caliber Carbine ~135 ft/lbs (183 joules) @ 760 fps
It is plainly obvious why so many recommend a 7.62x51mm NATO (.308 Win) chambered rifle as a primary defense rifle. It clearly overpowers all other modern, common military battle rifle calibers at all ranges and maintains a further effective range. The few negative aspects are the relatively higher recoil, louder report and heavier cartridge weight.
Keeping in mind the power of the aforementioned rifle calibers, and that the more powerful cartridges weigh more, and thus the shooter would be able to carry less ammunition when comparing a like weight (e.g. 25lbs) of ammunition. An average adult human male can only comfortably carry about a 65 lb load on their shoulders. An average adult human female can only comfortably carry about a 40 lb load on their shoulders. Keep that in mind when selecting a primary defense rifle.
Penetration is another important thing to consider. So is effective range and accuracy. Determine which pros outweigh the cons and pick your rifle(s) accordingly. By comparing the Big Three military calibers most commonly found in semi-automatic “battle” rifles in the U.S., I hope you have expanded your understanding a little bit on the amount of power they each bring to bear. If possible, I recommend getting at least one rifle in 7.62x51mm NATO (.308 Win) and another in either 7.62x39mm Soviet or 5.56x45mm NATO (or both if you can afford it). Heck, two of each is good too.
When it comes to the .30 Carbine cartridge and the M1 Carbine which fires it, many will pooh-pooh its lack of “stopping” power. Many of these same individuals will champion the .45 ACP as a great handgun cartridge. I know one is a pistol and one is a carbine, but the M1 Carbine more or less bridges the gap between a handgun and a battle rifle. At 200 yards, the M1 Carbine hits with the same power as the .45ACP does at nearly point-blank range. While the .30 Carbine cartridge in military configuration is FMJ (to abide to the Hague Convention of War [that restricts military use of expanding bullets], which at closer ranges can over penetrate a target and thus not release all of its kinetic energy, there are many commercially available sources which are loaded with JSP (Jacketed Soft Point) projectiles. These deforming bullets are essentially the same as most hunting bullets, though would be better as a personal defense weapon than a hunting one. Within the effective range, they will deform and ensure that most or all of the energy of the bullet is released in the target.
For defensive purposes, an M1 Carbine is still viable as a PDW (Personal Defense Weapon) in your battery–especially for small-statured women and adolescent children. A Ruger 10/22 (or Marlin 60/795) with Tech-Sights installed has a very similar length of pull, sight picture, and balance as an M1 Carbine. It can easily be used to train a person unfamiliar with firearms using the inexpensive .22LR cartridge until they prove proficient enough to graduate to a centerfire weapon–the M1 Carbine is the perfect transition weapon from the 10/22. It is more powerful and easier to control and has a greater effective range than most modern semi-auto handguns. While both the .30 Carbine cartridge and the M1 Carbine firearm are both fairly outdated, and there are better choices for a defensive rifle and cartridge, they are still better and more versatile than any semi-auto handgun, in my opinion. If you wind up seeing a WWII or Korean War era M1 Carbine from the CMP, at a gun show, pawn shop or from a personal seller and it is a reasonable price, I suggest looking into getting one. Also, a few modern reproductions are floating around out there by IAI (Israeli Aerospace Industries) and Auto-Ordnance (Both are good quality and American made). [JWR Adds: The Plainfield and Iver Johnson clones were also quite well made. The M1 Carbine reproductions to avoid were those made by Universal Industries. Few of their parts interchange with original GI M1 Carbine parts, and their trigger groups could best be descibed as “pot metal”. They were in fact more “look-alikes” than they were M1 Carbine clones.]
But when building your survival battery, make certain you can afford the necessary accoutrements for each rifle; such as magazines, spare parts, web gear/LBE, ammunition, lubricant/rust preventative, cleaning accessories, and most of all–training. Get familiar with safety first and foremost, and move your way into nomenclature and eventually to close, intermediate and long range shooting with each caliber in various shooting positions to broaden your horizons further. I also suggest that you pick up some grocery-store throw-away produce and line them up at varying ranges to see what kind of hydrostatic shock your rifle can produce at 400+ yards. Melons, pumpkins and coconuts are fun to shoot. They also put all the numbers above in perspective to what 1,000+ joules of force can do to soft tissue.
Let is all hope and pray that no one reading this will ever need to use any firearm in their battery against another human being. But if one day we find ourselves forced to defend our lives, family and property, then let us be prepared to stand and fight!
References:
Chuck Hawks’ Ballistics Page (Rifle Shooter magazine)
.308 Winchester Ballistics (Rifle Shooter magazine)
7.62×39 Ballistics (Rifle Shooter magazine)
.223 Ballistics (Rifle Shooter magazine)
.30 US Carbine Ballistics (Rifle Shooter magazine)
Wikipedia Page: Joule
Answers.com: Foot/Pounds
Baseball Pitching Facts and Fallacies
Rifle Shooter Magazine’s Ballistics Page
TKD Tutor: The Concept of Force
The cited energy and mass conversions done using Microsoft “Convert” utility program