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| The Great .308 versus .30-06 Debate |
 The Great .308 versus .30-06 Debate
A chat room discussion got me looking hard at the “.308 Winchester vs. .30-06 Springfield” debate. My contention was that there was no significant difference between the ballistics of the two in hunting situations, or for that matter in any other situation. So let’s examine the ballistics of both cartridges and compare.
First we’ll take a quick look at the history of both cartridges. The .30-06 Springfield started life as a US military cartridge in 1906. It was derived from the “.30 Model 1903” cartridge that was designed to replace the .30-40 Krag. The ’03 cartridge used the same 220 grain round nosed bullet as the .30-40. The ’06 is essentially the same case as the ’03 with a 150 grain spitzer bullet at 2800 ft/sec. The .30-06 was the primary cartridge for the US military until it was “replaced” by the .308 Winchester/7.62x51mm NATO in 1954. The .308’s original load was a 149 grain spitzer at 2800 ft/sec. Both cartridges have certainly been very successful in military, match and hunting use! (Reference “Handloading” by William C. Davis, Jr.)
To quote the Speer #13 manual, “In the hunting field, ballistic differences between the 308 and the 30-06 are negligible.” The .308 was designed to duplicate the .30-06 for military use, but in a half inch shorter package. Both guns use the same 0.308” bullets. These bullets range from 100 grains to 250 grains in various styles. I figured that the .30-06 would have an advantage as the bullets get over 180 grains because its case was originally designed for the heavier bullets.
The most common hunting bullet weights for these cartridges are the 150, 165 and 180 grain. I realize that there are tons of loads for each cartridge but you’ve gotta start somewhere. I looked in the Speer #13 manual and compared their loads for both cartridges. I figure this is a pretty good comparison as loads for both cartridges were fired in the same type rifle, a Remington 700 with a 22” barrel. In each case I took the bullet with the highest ballistic coefficient and the highest velocity listed.
Here is a chart of the muzzle velocities for each bullet for both cartridges, the difference between them (.30-06 minus .308) and the percentage of that difference:
Bullet weight .308 .30-06 Difference %
150 2919 2847 -72 ft/sec -2.5
165 2812 2803 -9 ft/sec -0.3
180 2623 2756 133 ft/sec 4.8
From the chart we can see that the average difference in velocities for the three bullets is 17 ft/sec, or 0.6%, in favor of the .30-06. Now don’t forget that these are average velocities. In a string of shots a cartridge/gun’s velocity can easily have a standard deviation of 1% or more. In other words the normal variations in loads result in a built-in error that pretty much means we can’t count on such a small difference to be meaningful.
So, what does all this mean downrange? We’ll zero both guns at 200 yards and compare the bullet energy there. Let’s also take a look at what the bullets will be doing at 400 yards, which is a heck of a long shot for hunting. I used the “PointBlank” ballistics program to make the comparisons.
With the 150 grain bullet the .308 has 2093 foot-pounds of energy at 200 yards while the .30-06 has 1985 foot-pounds. Out at 400 yards the .308 will have dropped 20.9 inches, and still has 1512 foot-pounds. The .30-06 will have dropped 22.13 inches and maintains 1428 foot-pounds. The .308 shows 5.9% more energy at 400 yards.
Then with the 165 grain bullet 200 yards the .308 shows 2202 foot-pounds versus 2187 foot-pounds for the .30-06. At 400 yards the .308 drops 21.90 inches and has 1645 foot-pounds. The .30-06 drops 22.06 inches with 1633 foot-pounds left. At 400 yards the .308 has a tiny 0.7% energy advantage.
Finally we take the 180 grain bullet, which should give the biggest advantage to the .30-06. At the 200 yard mark the .308 will have an energy of 2143 foot-pounds and the .30-06 will have 2379 foot-pounds. The .30-06 has about 11% more energy. When we get out to 400 yards the .308 will be 24.64 inches low and still have 1647 foot-pounds while the .30-06 will be 22.10 inches low and still carry 1840 foot-pounds. That means that at 400 yards the .30-06 has an 11.7% advantage in energy.
Now I’m sure that folks will look up their favorite of these two and “prove” that it is better in some manual or another. I looked in some other manuals too and found varying velocities. One thing I noticed in one manual was that, with 250 grain bullets (yes, that is two hundred and fifty grains), there was only 100 feet per sec difference in the velocities of the two cartridges. That particular manual doesn’t give any barrel lengths though.
Just for giggles I also looked at the .270 Winchester and .280 Remington loads in the same Speer manual. With a 22” barrel and a 150 grain bullet at 2907 feet per second the .270 has 2170 foot-pounds at 200 yards and 1648 foot-pounds at 400 yards, while dropping 19.98 inches. The .280, with a 24” barrel and a 145 grain bullet at 2975 feet per second, shows 2209 foot-pounds at 200 yards and 1689 foot-pounds at 400 yards, while dropping 18.83”. So, both of these cartridges “beat” the .30 caliber rounds in energy and trajectory.
When it’s all said and done does either the .308 or the .30-06 really have any ballistic advantage over the other? I’ll concede that an 11% difference in energy with the 180 grain bullet is an advantage but I wonder if a deer on the receiving end tell the difference between 1647 and 1840 foot-pounds of energy? Considering the overall differences and performance of both cartridges I’ll stick to my assertion that there is no SIGNIFICANT ballistic advantage with either cartridge. Now just pick which ever you like and enjoy shooting it! |
Posted by Pumpkinslinger on Tuesday, October 16, 2007 (18:29:48) (37517 reads) [ Administration ]
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