308 vs. 5.56 Caliber: Why the 308 is the clear winner over the 5.56 caliber

Trying to decide between the .308 Winchester and 5.56 NATO cartridges isn’t hard to do because these two rounds, except for military backgrounds, don’t have many other similarities.

As you probably know, the .308 and .223 calibers differ from their NATO spec equivalents, 7.62mm and 5.56mm, by maximum pressure allowance and internal dimensions, but for the sake of simplicity, we will use the names .308 Winchester and 7.62x51mm NATO interchangeably. The same will refer to .223 Remington and 5.56x45mm NATO designation too.

Since we don’t want to compare “apples and oranges,” the easiest way to choose one of these two calibers is to answer what use you intend for the rifle.

Obviously, the two cartridges belong to two entirely different categories but share the same originators – the U.S. Army. 

For all readers who love numbers, we have made an outstanding ballistics table with more transparent information and an easier way to compare data.

308 Vs. 5.56 Caliber
Cartridge .308 Winchester5.56x45mm
Bullet100 to 240 gr (6.48 to 15.55 g)90 to 130 gr (6.1 to 8.4 g)
Bullet diameter .308” (7.8mm)5.56 (.224”)
Case length2.015” (51.2mm)1.76” (45mm)
Maximum overall length2.8 (57.4mm)2.26” (57.4mm)
Rim diameter.472” (12.01mm).378” (9.6mm)
Max Pressure (SAAMI)62.000 psi52,000 psi
Muzzle Velocity150gr/ 2,820 fps55 gr/ 3,240 fps 
Muzzle Energy150gr/ 2,648 ft-lbs.55 gr/ 1,282 ft-lbs.
200yds Bullet Drop (inches)0.0”0.0”
Powder load46.5 gr25.0 gr
Rifle Weight6.0 lbs.6.0 lbs.
Free recoil energy 24.69 ft-lbs.4.68 ft-lbs.
Case capacity 56.0 gr H2O28.2 gr H2O

.308 Winchester

It’s a rule of thumb that most military cartridges bridged the gap from successful military service to worldwide sporting use. One of the two primary calibers for small arms in the U.S. military and NATO is 7.62x51mm (.308 Winchester), and the other is 5.56 x 45mm (.223 Remington).

The original 7.62x51mm cartridge was developed in the 1950s due to U.S. ordnance officers’ decision to replace the old one .30-06 Springfield in infantry rifles and light machine guns. Within a few years and many trials, they created the experimental T-65 cartridge based on the .300 Savage case that fired the same .308” bullet as the .30-06.

Soon, Winchester improved it and, in 1952, offered its civilian equivalent known as the .308 Winchester. Two years later, the U.S. military adopted the new 7.62x51mm NATO cartridge for its semi-automatic M14 battle rifle. 

Although the 7.62x51mm was purpose-built as a military cartridge, Winchester quickly noticed the potential of this powerful .30 caliber round for the commercial market and chambered their Model 70 bolt action rifle to the new ammunition. After some modifications, the commercial version of the military 7.62×51 was renamed in .308 Winchester.

While 7.62 NATO and .308 Win share cartridge dimensions, they are not necessarily the same. The 7.62x51mm cartridge case and the .308 Winchester are the same from an external dimension standpoint. However, the most significant difference is in barrel chamber length since military rifles in 7.62 are made with slightly longer chambers (longer headspace). The other differences are that the 7.62 case cartridge has thicker walls and smaller powder capacity resulting in higher chamber pressure. 

It’s important to note that due to chamber pressure differences between the .308 vs. 7.62 rounds, the .308 Winchester and 7.62 NATO cartridges can safely be fired in firearms designed for .308 caliber, but not vice versa. The opposite is true for .223 Remington in a 5.56 rifle, as the 5.56 is loaded to a higher pressure.

As the civilian form of the 7.62 x 51mm, the .308 Winchester followed the tradition of the all-American bore size – .30 caliber becoming even more famous than the legendary .30-30 Winchester or .30-06 Springfield.

Furthermore, if the measure of popularity for a particular cartridge is a number of newly created rounds based on its case, then the .308 Win ranks high on the list. For example, the .308 Win has spawned off the .243 Winchester, the .260 Remington, the .307 Winchester, the 7mm-08 Remington, the .338 Federal and a few others.

Since the 7.62x51mm NATO/.308 Winchester cartridge was more than powerful enough for military service rifles and modern battlefields it stayed very short in mainstream use, but the military continued to use it in general purpose machine guns (GPMG) and various bolt-action sniper-type rifles.

On the other hand, hunters and sportsmen throughout North America find that .308 Winchester loaded with new cartridge propellants provides nearly identical power to the venerable .30-06, but in a shorter package.

The .308 is an extremely capable hunter that became a primary big-game rifle in many American gun safes. As one of the world’s most popular big game hunting rounds, the .308 Winchester is available with bullet weights ranging between 100 to 240 grains. 

However, using three of the most common bullet weights for the .308, such as the 150 grain, 165 grain, and 180 grain, you will be able to hunt almost all medium and big game in North America. Besides, you can use your .308 rifle with excellent results on varmints and light-bodied game if you load it with lighter 110 to 130-grain bullets.

5.56x45mm

As already said for the previous cartridge, the 5.56 round was developed for military applications and shared a very similar arc with the longer .308 Winchester cartridge.

The .223 Remington was released to the commercial market in 1964 and later adopted for use in the new M16 rifles. The 5.56x45mm NATO cartridge was designed from the .223 Remington case by F.N. Herstal in 1970. Though 5.56 and .223 have identical case dimensions, they differ in allowable chamber pressure. The maximum allowed pressure by SAAMI for .223 Rem is 55,000 psi, whereas the 5.56 case was built to work with pressures of 61,000 psi. It means that you can shoot .223 Rem ammo in your 5.56 rifle, but you shouldn’t fire 5.56 NATO round from a rifle chambered in .223 Rem because the .223 rifle chamber is not rated to work with the pressure of a 5.56 cartridge.

At first glance, we notice some significant differences between the .308 Winchester and the 5.56 cartridges. First, 5.56x45mm has a significantly shorter overall length than the .308 Winchester (7.62x51mm) because the 5.56 was from the beginning intended for use in small black rifles (AR-15), that can only receive rounds up to 2.26″ long. 

For comparison, at 2.81″ overall length, the .308 cartridge is much longer and requires a larger rifle, though it is designed for short-action rifles common in the U.S.

Due in large part to the longer case length of the .308 Winchester, that cartridge has considerably more case capacity than the .223 Remington. Further, the .223 Remington uses .224″ bullets while.308 Winchester use .308″ bullets.

Being military cartridges, the .308 Win and 5.56 were primarily developed for semi- and full-auto firearms. That said, the .308 was chambered in M14 and various AR10-style rifles, and the 5.56 NATO cartridge was initially paired with the M16, a select-fire version of the AR-15 and later, it was chambered in many other Modern Sporting Rifles (MSR). Of course, the .308 Winchester and 5.56 quickly became available in many bolt action, pump, and semi-automatic rifle platforms.

The 5.56×45 NATO ammo can be purchased in bullet weights ranging from 36 to 90 grains, but the most common bullet weights are 55, 62, and 69 grains.

The 5.56 NATO is underpowered for many circumstances as its maximum effective range is about 400-500 yards. At 500 yards, the 5.56 drops about 5 feet with 312 foot-pounds of energy, while the .308 round has dropped approximately 48 inches but retained an energy level of 1,047 foot-pounds.

If you are planning to shoot beyond 500 yards, you should know the heavier .308 bullets will fight with the wind better than the lightweight .223 (5.56mm) projectiles.

Speaking of hunting, the .308 Winchester will likely serve you better if you could only have one caliber and want to hunt a variety of animals. 

On the other hand, the almost laser trajectory and modern hunting projectiles qualify the 5.56×45 as an extremely efficient round for hunting predators, thin-skinned animals and even whitetail deer and hogs. Furthermore, the low recoil impulse and flatter trajectory of 5.56/.223 Rem makes it ideal for marksmanship competitions and varmint hunters. However, you should know that some hunting regulations do not allow hunting with calibers smaller than 6mms.

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Final thought

As it said at the beginning of this short overview, these two calibers are on the two sides of a spectrum, and their advantages would be the best to use with the appropriate purpose.

If you are looking for a cheap and reliable cartridge to hunt varmints and paper target shooting, the 5.56x45mm is far the better option because it has a flatter flight path and ammo is cheaper.

On the other hand, the .308 Winchester has a clear advantage when hunting medium to big game because of heavier, larger in diameter, and generally much better-constructed bullets.

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