7.62x51 vs .308 – What’s The Difference? 

7.62x51 vs .308 – What’s The Difference? 
August 24, 2023 Edited August 25, 2023 2229 view(s)
7.62x51 vs .308 – What’s The Difference? 

I recently wrote an article that compared the .223 Remington to the 5.56mm. Folks were wanting to know the differences between the two, mostly could you shoot both from the same rifle. Matter of fact, you can read another article about that subject in this blog… it’s a pretty popular topic. 

Likewise, shooters want to know the difference between the .223’s larger cousins… the .308 and the 7.62x51. Where did they come from? Can you shoot both from the same rifle? We’ll get to that, but first, let’s take a look at the back story…

 

History

The .308 Winchester, as we officially know it, was “born” in 1952 (a good year as I was born then, too!). Anyway, the rifle cartridge was based on an experiemental series of military rounds called the T65, which were correspondingly based on the .300 Savage. The government was looking to replace the .30-06 round, which was getting long in the tooth, as the saying goes. There was nothing wrong with it, except that the case was very long due to the selection of powders available when it debuted in 1906 and it wasn’t the most efficient cartridge out there. The military wanted a new, more-efficient cartridge that could take advantage of newer powders and which would have a shorter case. So, the .300 Savage was the model for the T65. Later versions of this experimental cartridge used a slightly longer case that provided ballistics roughly equal to the venerable .30-06. That cartridge was T65E5.

Winchester took note of this development and decided that it would fill a niche in the hunting ammunition market. So, they released their version in the year I mentioned above, 1952. It wasn’t until two years later in 1954 that the 7.62x51 became a NATO cartridge, based on the T65E5 experimental round. As they say, the rest is history - the .308 has become the most popular short-action big game hunting round across the globe. I can’t say that the 7.62x51 NATO was literally based on the .308 Winchester, but the military would have noticed how popular the round was, and how efficiently it did its job. The culmination of the T65 experiments paid off by giving us two excellent .30-caliber rounds. 

Here’s an anomaly – this cartridge bucks the norm. The military version came after the civilian cartridge, unlike most other civilian/military rounds. Typically, the military version predates the civilian one. Not so here!

 

Differences… Can I Shoot Both In My 7.62x51-Chambered Rifle?

In a word, no. Why, I hear you ask? Really, why can’t you shoot both in your NATO-chambered boomer? Because you might have your .308 cases rupture. Because of spec changes from 1952 to 1954, the .308 lost a tiny bit of headspace room… plus the case walls are thinner than the 7.62’s. That means that the case may stretch when fired in the ever-so-slightly larger military chamber and lead to the possibility of a case rupture. 

308 and 7.62 case

Image: targetbarn.com

.308 case (left); 7.62 case (right). Notice how much thicker the 7.62’s case walls are? If you CAN see the difference, you have better eyes than me! The case is thicker but you can’t see the difference. You also can’t see the difference in case length… the 7.62’s case can be up to .0010” longer.

Here’s a good place to stick the chamber dimensions images, both courtesy of wikipedia:

 

308:

308 chamber dimensions

 

7.62x51

7.62 chamber dimensions

 

As you can see, not much difference… just enough to exhibit some caution.

So, yes, Virginia, you can fire 7.62 NATO from a .308-chambered rifle but I’d be cautious about going the other way with it. Granted, the odds of you having a case blow up might be small, but why risk it? With the 7.62’s extra headspace and slightly-wider chamber walls, the .308 may not not a good fit in some 7.62 chambers.

Probably the best course of action you should take would be to check with your rifle’s manufacturer about whether it’s safe to shoot both calibers from your particular rifle. Better safe than sorry!

 

.308 vs 7.62x51 Ballistics

The ballistics between the two rounds are similar. First, we need to remember that the .308 is loaded to higher pressure than the 7.62 (62K PSI vs. 60K PSI)... that in itself is backwards among military-to-civilian cartridge development. Usually, military versions are loaded to higher pressures. Again, with the anomalies…

I searched and searched for comparison tables of bullet drop for both of these rounds but couldn’t find one. It seems that folks who make up such images lumped both the .308 and the 7.62 together. Granted, the .308 runs to slightly higher pressures than does the 7.62, but given the 7.62’s thicker case walls, it becomes pretty much of a wash. The main point is, if you want to move a 150-grain bullet at close to 3,000 fps, then either of these calibers would work for you. 

To sum it up, here’s a .308 trajectory table from longrangehunting.com. It is here only as an example of what types of velocities you can expect from the .308, or the 7.62x51 for that matter. It uses a 165-grain bullet out of a (short) 18” barrel… more speed would be gotten from a longer tube, no doubt, But it’s an interesting table to look at. For example, at 250 yards, your sight elevation is just 1.4 inches up, and at 500 yards, you’re only talking about 10 inches. Not bad for a common hunting round.

308 vs 7.62 ballistics

Conclusion

If you want a decent hunting cartridge for pretty much all-round use, you can’t go wrong with either of these rounds. There have been many newer calibers introduced in the 70-plus years since the .308 was introduced, but both the .308 and 7.62x51 have been proven and have stood the test of time…one in the hunting field and the other on the battlefield. 

Just remember what we said about firing both from a .308-chambered rifle… yup, do it. But, be careful if you have a gun chambered in 7.62x51. It’s all got to do with case dimensions – headspace and case wall thickness. Chances are you won’t have any problems but please be aware of it. 

From speedy, light bullets meant for varmints to great big ol’ moose-stompers, these .30-caliber rounds will do it all. Let’s hear about your experiences with them below!

 

  

 

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Bob Sedam
October 15, 2023
Great information to know. Thank you
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