Since its inception, there has been an ongoing debate as to whether the 308 Winchester is a superior cartridge over the 30-06. Although this article will not settle this age-old debate once and for all, it should provide some insight on some of the benefits that these cartridges have over each other.
As far as similarities go, the 308 Winchester and the 30-06 do not share many. Perhaps the biggest similarity, which is primarily why there is even a debate in the first place, is that they share the 30 caliber bore size. Both cartridges utilize 0.308” diameter bullets, meaning that stocking up on this size would be useful for reloading either cartridge.
Along with sharing the same bore size, the 308 and the 30-06 share the same rim diameter (case head) of 0.473”. This is the same case head size used by many standard short action offerings as well as nearly all standard long action offerings. With this case head size, both cartridges almost exclusively use large rifle primers.
Now that we have the similarities out of the way, how do these cartridges compare?
In terms of appearance, it is obvious that the 30-06 stands much taller than the 308 Winchester. At a nominal case length, an empty 308 case stands at 2.015”. An empty 30-06 case on the other hand, stands at 2.494” which translates to a 23.8% increase in length over the 308.
As you might expect, this additional length gives the 30-06 a large edge in terms of case capacity. The 308 Winchester has a case capacity of approximately* 56 grains of H2O. The 30-06 on the other hand, will hold approximately* 68 grains of H2O, or 12 grains more than the 308. This translates to an increase in capacity of H2O (not usable capacity) of about 21.4% more than the 308, which is substantial.
Contrary to common belief, however, extra length is not always a benefit. All this extra length comes at a cost, which is primarily weight. A spent 30-06 casing weighs approximately* 12.7% more than a spent 308 casing. A factory loaded 30-06 cartridge weighs approximately* 10.4% more than a 308 with the same components.
Due to its increased length, the 30-06 is limited to long actions whereas the 308 is almost exclusively chambered in short actions. Short actions provide less bolt travel for faster follow up shots, along with the added benefit of weighing slightly less than long action counterparts.
Now that we have gotten these specs out of the way, how do these cartridges compare in terms of performance?
Typically, factory loaded 30-06 ammo will land somewhere between 100-150 feet per second faster than the 308 Win when using the same bullet weight. Some load offerings may fall slightly outside this range, though it should be a good estimate. In general, lighter projectiles will fall on the low end of this range, whereas heavier projectiles typically fall on the higher end of this range.
If we take a look at a 150-grain soft point fired from the Federal Power Shok line of ammo, we see that the 308 Win has a muzzle velocity of 2820 feet per second. Using the same line of ammo and bullet weight, the 30-06 has a muzzle velocity of 2910 feet per second. This is only an increase of 90 feet per second or about 3.2% over the 308.
With a 178 gr ELD-X fired from the Hornady Precision Hunter Line of ammunition, the 308 Win has a muzzle velocity of 2600 feet per second. Using this same line of ammo and bullet weight, the 30-06 has a muzzle velocity of 2750 feet per second, which is an increase of 150 feet per second or about 5.8% over the 308.
A 5.8% increase does not seem like all that much, so how does it translate in the field?
At 100 yards, the 30-06 retains 5.9% more velocity than the 308. At 500 yards this number jumps to 6.7% and at 1000 yards the 30-06 retains 6.8 % more velocity than the 308.
At 100 yards, the 30-06 retains 12.2% more kinetic energy than the 308. At 500 yards this number jumps to 13.7% and at 1000 yards the 30-06 retains 14% more kinetic energy than the 308.
With a zero value of 100 yards, the 30-06 is 13.2% flatter shooting than the 308 at 500 yards. At 1000 yards, this value drops slightly to 12.7%.
*Values were gathered using a ballistic app with a reference value of sea level at 80 degrees Fahrenheit with 78% humidity.
Compared to factory-loaded ammunition, the 30-06 generally gains slightly more velocity when reloaded. With standard load recipes from reputable sources, the 30-06 is generally between 150-200 feet per second faster than the 308.
With its somewhat limited case capacity, the 308 Winchester is not optimal with bullets weighing over 175 grains. Typically, the heavier a bullet, the longer it will be. This increased length must go somewhere, which starts to eat into the 308 Winchester’s somewhat limited case capacity.
With a healthy increase in case capacity, the 30-06 shines over the 308 when using heavy projectiles. With a proper powder and bullet combination, the 30-06 can fire projectiles up to 220 grains at reasonable velocities. Bullets of this weight can be more effective on larger game, though they will not have as flat of a trajectory as most lighter projectiles.
When choosing a rifle cartridge, one of the biggest factors to consider is whether there is a rifle offered that will fit your needs. Although, it would be hard to walk into a gun store and not find a rifle chambered in either one of these cartridges, the 308 Winchester has a major advantage when it comes to options.
When it comes to bolt action rifles, both cartridges are very popular chamberings. Although the 30-06 is a very popular bolt action offering, it is limited to standard long actions which are not produced by every manufacturer. As a short action cartridge, the 308 Winchester is offered in a wider range of bolt action rifles.
In terms of semi-auto rifles, the 30-06 is not a very popular offering, especially in new production rifles. The 308 on the other hand, is currently one of the most popular calibers chambered in semi auto rifles. With the vast number of AR-10 style rifles, along with many other platforms, it is easy to see why.
When it comes to ballistics, there is no denying that the 30-06 outperforms the 308 Winchester. Regardless of bullet weight, the 30-06 will be faster than the 308 (though it may only be marginally with lightweight bullets). If you are dead set on using bullets heavier than 175 grains, the 30-06 is a clear winner if ballistics is the only metric you’re after.
The question becomes whether this slight advantage in ballistics is enough to compensate for the weight savings and compactness of the 308. Along with these benefits, the 308 Winchester has an almost endless number of rifles (especially semi-auto) available to fit almost exactly what you need.
Either way you look at it, both cartridges have some benefits over each other. It would be hard to make a bad choice with the 30-06 or the 308 Winchester as both cartridges have earned an excellent reputation over the years.
*The case capacities listed represent the approximate amount of H2O that will fit inside an empty case. These values can vary based on the manufacturer as different companies will typically result in slightly different case capacities.
The case weight percentage difference is based on Federal Champion head-stamped casings. The ammunition weight percentage difference is based on Federal Fusion 165 gr soft point loads in each cartridge.