Compared: The .308 Winchester and .303 British
By Chuck Hawks
The .303 British served the Armed Forces of the United Kingdom and its Commonwealth partners as their standard infantry rifle and machine gun cartridge through two world wars and innumerable smaller conflicts, including the Boer War and the Korean War. The .308 Winchester was adopted by the US military and NATO as the 7.62mm NATO in the 1950's, after its introduction by Winchester as a hunting cartridge, and has been on active duty ever since as a service rifle and machine gun cartridge. Interestingly, the UK adopted the .308 to replace the venerable .303 in 1957, in order to conform to the NATO standard. Both are in use in Iraq and Afghanistan today, prized by Allied soldiers and Muslim radicals alike for their long range stopping power compared to the attenuated 5.56mm NATO and 7.62x39 Soviet assault rifle cartridges commonly used by the opposing forces.
More importantly to the readers of Guns and Shooting Online, both the .308 and the .303 have been successful big game hunting cartridges, used around the world. They are classic CXP2 and CXP3 game cartridges that, along with the American .30-06 Springfield and German 8x57mm Mauser, practically define the term "all-around big game cartridge." These two cartridges are covered individually in articles on the Rifle Cartridges page. The .303 British is widely (but loosely) compared to the .308 Winchester by less credible online sources, hence this article to see how they actually stack-up.
The .308 Winchester has a .300" bore diameter and uses .308" diameter bullets, while the .303 British has a .303" bore diameter and uses .311"-.312" bullets. Thus, the .308 is named for its bullet/groove diameter, while the .303 is named for its bore diameter. The .303 is actually the larger caliber, by a small amount. In modern terms, the .308 actually shoots .30 caliber bullets and the .303 shoots .31 caliber bullets.
A significant difference between the two is that the .303 is a rimmed, bottleneck cartridge with a lot of body taper and a shoulder angle slightly less than 17-degrees. Visually, it shows its age and its rimmed case is not readily adaptable to Mauser type, double column magazines. This has limited its popularity in modern sporting rifles, since practically all use some sort of double column box magazine. Despite this, .303 ammunition remains a strong seller, due primarily to the great number of surplus Lee-Enfield military rifles that have been released to the public. Many of these rifles have been sporterized and some are even hunted in original condition.
The .308 is a modern looking, rimless, bottleneck cartridge with a 20-degree shoulder and little body taper. It was designed specifically to function easily in semi-automatic rifles with detachable, double column magazines. The .308 case is a very efficient design and a number of successful cartridges have been based on it, including the .243 Winchester, .260 Remington, 7mm-08 Remington, .338 Federal and .358 Winchester. Practically every hunting rifle that can chamber the .308 is offered in the caliber and it is among the top five best selling cartridges.
Typical .308 military ammunition launches a 150 grain FMJ spitzer bullet at a muzzle velocity (MV) of 2750 fps. Typical .303 military ammunition launched a 174 grain FMJ spitzer bullet at a MV of 2440 fps. Modern .308 hunting ammunition is usually loaded with 125, 150 grain, 165 grain or 180 grain bullets. Modern .303 hunting ammunition is usually loaded with 125, 150, 174, 180 or 215 grain bullets.
150 grain bullets are available in both calibers, are a good choice for both calibers and the seventh edition of the popular Hornady Handbook of Cartridge Reloading lists loads using 150 grain bullets for both cartridges, so this comparison will be based on maximum or near maximum Hornady loading data for 150 grain bullets, which is very similar to typical factory load data for the .308/150 (MV 2820 fps) and .303/150 (2690 fps). This article will compare the .308 and .303 based on velocity, energy, trajectory, killing power and recoil. The ballistic coefficient, sectional density and cross-sectional area of 150 grain .30 caliber (.308") and .303 caliber (.312") bullets are so similar that, for big game hunting purposes, they can be disregarded.
Velocity is one of the common criteria used to compare rifle cartridges. It is the most important factor in calculating kinetic energy and, other factors being equal, significantly flattens trajectory. Some feel that a high velocity bullet impact creates a "shock" effect on the animal's nervous system that can result in rapid incapacitation or death, although this is not proven and not all authorities agree with this thesis. Here are the velocities in feet-per-second (fps) for maximum loads using 150 grain bullets at the muzzle, 100, 200 and 300 yards.
The .308 has a 100 fps advantage at the muzzle, but this shrinks to 40 fps at 300 yards. This is not completely insignificant, but it is not a major difference, either. We will soon see how much advantage its velocity advantage gives the .308 in terms of downrange trajectory.
Kinetic energy powers bullet penetration and expansion and is a major component of killing power. Energy is expressed in foot-pounds (ft. lbs.). Here are the kinetic energy figures for our two loads from the muzzle (ME) to 300 yards.
The .308 is superior to the .303 in terms of kinetic energy, although not greatly so. If, as is sometimes stated, an elk bullet should be carrying at least 1200 ft. lbs. of remaining energy at impact, then these are competent elk cartridges. In fact, both the .308 Win. and .303 British have accounted for a large number of elk and similar size animals around the world. Usually bullets in the 165-180 grain range would be chosen for hunting large animals, but the power is clearly there in both cartridges.
The flatter the bullet's trajectory, the easier it is to place accurately at extended ranges. Since bullet placement is of over riding importance in killing power, a reasonably flat trajectory is important to the hunter. Here are the trajectory figures for our two cartridges based on a 200 yard zero with scoped rifles.
Once again, the .308 Winchester proves to be the superior performer, but not by much. A ½" difference in bullet drop at 300 yards is unlikely to be noticed in the field.
There have been many attempts to quantify and compare the killing power of rifle bullets. One of the most recent, and among the best, is Hornady HITS (Hornady Index of Terminal Standards). It considers multiple factors including 100 yard impact velocity, bullet weight, sectional density and bullet diameter to derive a 100 yard killing power score. HITS have a positive correlation with reality and are easily calculated on the Hornady web site. Cartridges and loads that score less than 500 HITS are suitable only for small game; cartridges/loads that score 501-900 HITS are for medium size game (CXP2); cartridges/loads that score 901-1500 HITS are for large game (CXP3); cartridges/loads that score in excess of 1500 HITS qualify as dangerous game (CXP4) cartridges. Here are the HITS scores for our two comparison loads.
As you can see, the killing power of both loads is in the upper realm of medium game (deer, antelope, sheep, goats and black bear) cartridges, which is what you would expect from 150 grain bullets in these cartridges. Switching to 165-180 grain bullets will elevate them to the large game category, hence their reputation as all-around hunting cartridges.
Since the momentum of every action must equal the reaction, recoil is the price we must pay for shooting. Recoil is poisonous to accuracy and must be carefully considered when selecting a hunting rifle/cartridge combination. The inherent killing power of any hunting rifle is moot if the shooter cannot get the bullet into the animal's vitals. Here are the approximate free recoil energy (in ft. lbs.) and velocity (in fps) figures for our comparison cartridges fired in nine pound rifles.
As with the other performance categories, there is not a great difference between the two loads. What difference there is, this time, favors the .303 British. Slightly lower ballistics also means slightly less recoil.
Summary and Conclusion
This comparison shows that the .308 Winchester has an advantage in ballistics across the board. However, the .308's downrange advantage is slender and those who state that the two cartridges are similar in performance are basically correct. It would be difficult to postulate a reasonable big game hunting scenario where the .308 was markedly superior to the .303. It would seem that when the United Kingdom switched from the .303 to the .308 for their military rifles and machine guns, they gained very little in terms of performance.
It is a different story in terms of cartridge design, as applied to repeating rifles. The shorter, rimless .308 cartridge is much better adapted to modern selective fire weapons with interchangeable box magazines. Winchester's creation is based on a superior case, which accounts for its overwhelming popularity in modern rifles, both military and sporting. .303 British cartridges, due to their rimmed case, must be loaded in magazines so that the rim of each cartridge is always in front of the rim of the cartridge directly below it in the magazine. Neglecting to do so will result in a failure to feed that ties-up the rifle. The rimless .308 case has no such requirement and .308 cartridges can be rapidly thumbed into a magazine without regard to precise rim positioning. This makes the .308 faster to manually reload and more reliable in operation.
Perhaps more important in the overall scheme of things for the sportsman is that a better selection of .308 factory loaded ammunition is more widely distributed across North America. .303 factory loads are reasonably available, but .308 ammo is more available. In addition, .303 British rifles are largely restricted to military surplus Lee-Enfields or sporterized versions of the same, but practically every model of factory built hunting rifle is available in .308 Winchester. On both the new and used gun markets, the selection of .308 rifles is incomparably better.
If you are buying a new rifle, the .308 Winchester is clearly the way to go. If all you can afford is a military surplus rifle, the Lee-Enfield SMLE in .303 British is one of the better choices. It is a potent, proven cartridge and its ammunition is more widely distributed than most of the other surplus military rifle calibers.
Copyright 2010, 2012 by Chuck Hawks. All rights reserved.