7.62 NATO vs .308 Winchester Ammo, What’s The Difference?

Tom McHale, dangers a battle to elucidate the refined nuances between 7.62 NATO vs .308 Winchester Ammunition.

If you wish to begin a superb bar battle, ask a saloon stuffed with gun individuals concerning the variations between .308 Winchester and seven.62x51mm NATO. We’re going to dive into the fray with a simplified and sensible clarification. Prepared?

They’re totally different.
They aren’t totally different.
They could be totally different.

OK, in order that was a little bit of a clever man response, however these statements are all fairly true. Don’t fear, we’ll clarify it additional. Nevertheless, we’re going to attempt to do this in such a means that you just don’t need to bash your individual brains out by having to learn concerning the nuances of issues like piezo transducers.

Let’s take a look at a number of classes of comparability, then we’ll sum issues up.

7.62 NATO vs .308 Winchester – Historical past

Throughout the Forties and early Fifties, navy rocket surgeons needed to enhance the effectiveness of the M1 Garand rifle and its .30-06 cartridge. One contender, extra appropriate for increased capability field magazines was a modified .300 Savage design referred to as the T65. Whereas specs different all through growth, it ended up because the earliest iteration of the 7.62x51mm NATO. However, as regular, the industrial market was extra nimble, and Winchester launched the .308 Winchester in 1952.

It took the federal government till 1957 to have a cartridge and rifle hitting the barracks with related specs.

7.62 vs .308 – Strain

Right here’s the place a number of the confusion comes into the image. Most strain numbers thrown round for the 2 calibers are sometimes proven as 50,000 “psi” for 7.62 and 62,000 psi for .308. At first look, that seems to be a giant distinction and a possible motive why people may take into account it unsafe to fireplace a “increased strain” industrial .308 cartridge in a rifle constructed for 7.62x51mm NATO.

As with most issues, the satan is within the particulars. I put that fifty,000 “psi” quantity in quotes as a result of it’s mistaken, a minimum of when proven with a kilos per sq. inch label on the finish. That fifty,000 quantity is definitely an correct illustration of copper items of strain or CUP. A far much less exact technique to measure strain, the strategy actually depends on taking a look at how a lot little copper disks compress whenever you hearth the gun. Whereas there isn’t a constant mathematical system that equates CUP to kilos per sq. inch (PSI) throughout the board, the distinction on this particular case is someplace round 8,000. In different phrases, the utmost strain for 7.62x51mm NATO is about 58,000 psi – not all that removed from the 62,000 determine for industrial .308 Winchester.

As each hundreds are routinely proof examined at far increased ranges, this 4,000 isn’t a distinction that’s going to change the trajectory of Michael Moore’s every day Krispy Kreme run.

7.62 NATO vs .308 Win – Case thickness

Measuring the thickness of cartridge circumstances is type of a ache, particularly since I are inclined to mash all of them up when attempting to chop them in half with my Dremel instrument. So, I took the shortcut as an instance the distinction. From my huge bucket of .308 / 7.62 brass, I chosen some consultant samples of each industrial .308 Winchester and seven.62x51mm NATO brass and weighed them. I picked a number of of every and averaged the weights. I didn’t measure the circumstances as a result of they’ve been fired, in order that gained’t inform me a lot apart from the overall dimension of the chamber from which they went bang.

Hornady .308: 169.6 grains
Winchester .308: 163.3 grains
Lake Metropolis 7.62x51mm NATO: 183.5 grains

That’s a major distinction! Thicker partitions mixed with related exterior dimensions means much less powder capability and a decrease “prime finish” and all else the identical, decrease strain and velocity.

The thicker brass of seven.62 circumstances is a major issue for the rationale we’ll focus on subsequent.

7.62 NATO vs .308 Winchester – Headspace

Final however not least we get to the true distinction. Army rifles for 7.62x51mm NATO can, and normally do, have longer chambers. In issues like machine weapons powered by ammo made everywhere in the world, there’s acquired to be some slack for dependable feeding and operation with all that violence occurring through the feeding and ejection course of. The answer is to make the chamber headspace a bit longer. If you happen to’re not acquainted with headspace, consider it as the space from the bolt face to the purpose within the chamber that stops the ahead movement of the cartridge case. If the chamber headspace is just too lengthy for a cartridge, it’s going to float forwards and backwards within the chamber. If the headspace is just too small, the bolt is not going to shut correctly or would require extra drive to shut.

How a lot totally different is the headspace? The .308 Winchester chamber headspace is between 1.630 and 1.6340 inches (SAAMI Data). The 7.62x51mm NATO is between 1.6355 and 1.6405 inches. Whereas the printed numbers present about six-thousandths of an inch distinction, it’s common for the headspace in a surplus 7.62 rifle to be 10 and even 15 thousandths longer than that of a industrial .308. That doesn’t sound like a giant deal, proper as much as the purpose the place you hearth thinner industrial brass in a long-chambered rifle. The brass will stretch, presumably sufficient to contribute to a harmful case rupture. Doing the identical factor with thicker navy brass is not any huge deal and the way in which the system was designed. Thicker brass can deal with some further stretching into an extended chamber throat, so it’s no huge deal.

The answer to the query is to know your rifle and what its headspace actually is. Solely then will whether it is protected to shoot industrial .308 Winchester ammo in a 7.62 chamber.

Determining in case your headspace is protected is a reasonably easy deal. You may order a set of .308 Winchester Go / No-Go headspace gauges. After eradicating extractors and/or ejectors as acceptable as a way to take away all sources of rigidity, use the gauges to verify the chamber dimension. The bolt ought to shut simply on a Go gauge and never shut on a No-Go gauge. A 3rd sort, a Discipline Gauge checks the utmost printed chamber dimension. With some 7.62 rifles, you may discover that the bolt closes on the No-Go gauge. So long as the bolt gained’t shut on the Discipline gauge, you’re nonetheless inside most printed limits.

The online-net-net

Technically talking, when it comes to specs, there are variations, however primarily within the chambers of rifles designed to fireplace every cartridge. 7.62 brass is a bit thicker, and industrial .308 is typically loaded to barely increased strain, however apart from that, the cartridges themselves are just about the identical.

If you wish to be ultra-safe and conservative, hearth solely 7.62x51m NATO in 7.62 chambered rifles and .308 Winchester in .308 rifles.

Subsequent on the “danger” spectrum is the situations of utilizing 7.62x51mm NATO ammo in a .308 chamber. In principle, you may run throughout ammo that’s significantly lengthy. Ammo won’t chamber in any respect or may require undue strain to the chamber. That might end in dangerously excessive strain. In actuality, that might be actually uncommon. Whereas 7.62 ammo could possibly be considerably longer, that’s a reasonably uncommon factor, a minimum of to a major degree, so most individuals don’t take into account it a giant deal to make use of 7.62 ammo in a .308 chambered rifle.

The place that you must watch out is utilizing .308 Winchester industrial ammo in a 7.62x51mm NATO chambered rifle.

Whereas most fashionable 7.62 chambers are most likely effective as they are usually minimize nearer to .308 dimensions, it’s at all times most secure to know precisely what you’ve when it comes to headspace. In case your rifle has lengthy headspace, follow 7.62 NATO ammo – don’t use industrial .308.

About

Tom McHale is the writer of the Insanely Sensible Guides e book collection that guides new and skilled shooters alike in a enjoyable, approachable, and sensible means. His books can be found in print and eBook format on Amazon. You may as well discover him on Google+, Fb, Twitter and Pinterest.