THE ROUND THAT WON THE WORLD
It took me a long time to decide which cartridge to focus on in my next article. I have been always convinced that there is not much more to say about .308 anymore. However after browsing through different resources, I found out that there are not too many articles that would actually point out some of the things that I consider important. So I decided to provide you with compiled resource about .308’s history, parameters and performance in different situation it is being put into.
.308 Winchester started its life in early 1950’s as cartridge developed for military use within NATO. Its original designation is 7.62×51, which refers to the dimensions of the cartridge (diameter of rifling X length of case) in millimeters. On the other hand, civilian version of the “same” cartridge, .308 Winchester, takes its name from the bullet diameter in inches (7.82 mm). Nevertheless, cartridge got to the civilian market under .308 designation in 1952. Ironically, two years prior to its introduction in US military. And so began the life of one of the most successful and versatile calibers of 20th century.
Despite above described facts, .308 and 7.62×51 are not 100% identical. Due to different specifications registered within SAAMI & Military norms, very minor differences in parameters can be found.
As can be seen on the picture above, length at which conus starts to develop on the brass is different, creating 0.013 inch difference which may cause minor chambering issues. One of such examples might be problems in chambering of reloaded rounds in civilian .308 Winchester rifles, after cartridge was fired in 7.62×51 NATO chamber and was not fully resized during reloading process. Exact differences can be seen on the dimensions of gauges which are used for measuring correct dimensions of the chamber, when being drilled into the barrel.
.308 Winchester (SAAMI) Gauges
GO – 1.6300″
NOGO – 1.6340″
FIELD – 1.6380″
7.62×51 Military Gauges
GO – 1.6350″
NOGO – 1.6405″
FIELD – 1.6455″
Second difference can be found in the case construction, as military brass (7.62×51) is designed to function in wide variety of conditions, different temperatures and most important of all – nobody in military plans to reload the brass. Because of that military ammunition has usually much thicker case walls which allow safe expansion in slightly bigger chambers in rifles designed with bigger tolerances or even severely worn out chambers. This difference may prove problematic if you are trying to use commercial .308 ammo in 7.62×51 chamber, especially one which was worn out or made with bigger tolerances. SAAMI also allows loading of cartridges to higher pressure – 62 000 PSI, in comparison with military norm – 58 000 psi. Above mentioned facts can lead to major issues, including case rupture and thus endanger safety of the shooter.
Despite of this, such situations are extremely rare and can occur mainly in case of very old firearms. Even SAAMI considers both cartridges to be safely interchangeable, however I would advise to take this into consideration, especially in case that you are using very old bolt actions or semi autos, which might be weakened by years of use.
PERFORMANCE AND USE IN HUNTING
When comparing .308 with its closest competitor and predecessor in military – mighty .30-06 you can easily find out that despite considerable difference in length, .308 is almost on pair when it comes to muzzle energy and velocity. The difference is usually between 8-15%. To put this into perspective, average muzzle energy of commercially produced .308 fired from 24 inch barrel would be about 3600 Joules (2650 ft-lbf) while commercial .30-06 will produce around 3950 Joules (2910 ft-lbf) under the same conditions.
This is very minor power loss for .308, especially taking into consideration its main advantage – ability to fit into much shorter action, especially on bolt action rifles. Because of that, rifles chambered in .308 are usually slightly shorter than their .30-06 counterparts. This brings major benefits for any hunter – especially if you are forced to maneuver through the thick brush or hunting driven game, when pointability of rifle brings many advantages.
If you own .308, you are going to be able to use amazing variety of ammunition. Most of the bullets which will be used for hunting are within the weight range of 140-180 grains, however .308 can be effectively used with bullets as light as 120 grains or as heavy as 220 grains. This of course may require different twist rates, nevertheless, it is possible.
Speaking about twist rates, in most .308 barrels you can find rifling which ranges from 1:10 to 1:12, which are well suited to be used with bullets from 130 grains to 180 grains. If you would like to even heavier bullets, many aftermarket producers offer barrels with much faster twist rates for stabilization of very long bullets with better BC. Nevertheless, these usually find place in shooting competitions and not practical life. (not taking into account that .308 is being replaced by cartridges in 6.5 in long range and accuracy competitions around whole world). Also use of long high BC bullets either requires smaller powder charge, in order to avoid its compression. Alternatively good gunsmith will be able to touch up your chamber and lengthen “freebore throat lead”. However this renders rifle pretty much unusable with lighter bullets and thus makes .308 much less versatile than it was meant to be. What a pity..
Above mentioned facts make .308 Winchester one of the most universal cartridges out there. While light 130 grain bullets can be used for varmint & pest control, heavier bullets can be used on wide variety of medium and big game. Bullets with very good BC and soft construction can be found very easily as well, turning this cartridge into 800 or even 1000 meter long range tool in hands of capable shooters.
OFFSPRINGS OF .308
You do not need to be rocket scientist to correctly assume that based on above mentioned parameters and advantages over its predecessors, .308 turned into platform for experimentation. Just by necking up or down the case, multiple different calibers have been developed.
First to mention needs to be smallest of them all – .243 Winchester, which utilizes 6 mm caliber bullet. This cartridge is one of the most popular in case of most gun manufacturers and provides very flat trajectory, especially in case of initial 200 meters. It had been widely used since its introduction in 1955 to hunt medium game around the world.
.260 Remington is one of younger offspring. Introduced in 1997, it is utilizing 6.5 millimeter bullets, providing slightly more powerful alternative to popular 6.5×55 SE, especially in case of use with heavier bullets. 6.5 mm bullets are among the most popular when it comes to hunting and competition shooting, so it is only logical addition to the .308 case family.
7mm-08 Remington had been introduced in 1980, and as the name suggests, it is cartridge which utilizes .308 brass necked down to use 7mm bullets. They are often used in fast twist rate barrels, which allows use of long, high BC bullets, with high sectional density. This of course leads to very reliable and dependable hunting performance.
.338 Federal is one of those calibers, I dream about owning. It had been developed by Federal and SAKO and introduced in 2006. This cartridge is utilizing heavy bullets which can produce higher energies than .30-06 – some of the commercially loaded ammunition can produce as much as 4350 Joules (3210 ft-lbf) of energy in 24 inch barrels (equivalent of 7 mm Remington Magnum), providing great tool for big game hunter, especially in case of bears or wild boars.
.358 Winchester is one of the cartridges which did not fare well, despite its early introduction in 1955. It was supposed to provide alternative to old and time proven .35 Whelen, however it failed to hold on the wave of .308 case popularity and rifles and ammunition for this caliber can be found very rarely.
.357 Winchester and .307 Winchester are calibers which were based on .308 case, however their rim was adapted to be used in lever action – are considered to be semi-rimmed. Both were introduced in 1982, however their popularity and availability is limited as well.
.308 Winchester is tremendous cartridge. As I already stated, it is very popular, yet it does not excel in anything, except for its versatility. Nevertheless, if I needed one rifle to do it all, it would be definitely bolt action chambered in .308. Not only due to its performance, but also due to ammunition availability and variability, good barrel life and shorter overall length, which allows very fast bolt cycling. Despite the fact that it is losing on the shooting ranges against the 6, 6.5 and 7 mm cartridges, it is hardly skipping a beat among hunters or tactical shooters. And it will stay like that for a long time to come.