Author’s Introductory Disclaimer: While I am a long-time reloading enthusiast, my advice and insights are not substitutes for the information found in reloading manuals. So do confirm any information herein and draw your own conclusions.
Introduction
I have discovered over the years that many shooters are planning to use incorrect ammunition in their military rifles that with repeated use over time would ruin the rifle’s mechanism, or if the rifle should be used in battlefield conditions, the rifle for many reasons could fail them just when they needed to defend themselves.
Few are acquainted with using their rifles in actual battlefield conditions where the rifle experiences excessive heat and dirty conditions. Sadly the industry fails to adequately educate civilian riflemen. The difference and the problems that can occur however, do mostly apply to other rifles chambered in military cartridges that also have a commercial variant.While I am not an expert in any field, this opinion is not unsubstantiated. There is more than adequate technical information available on the internet that can be discovered. As this article is written in haste, it is not possible to reference this material as I have only a few hours to complete this article and no internet access at home that would allow me to provide links to substantiate my opinion. I am however an enthusiastic reloader of many decades who has an eye for technical details and information that is not often if ever discussed by the general public.
I am a serious hobbyist who has also repaired some of the popular military rifles out there such as the AR-15, AR-10, M1 Garand, and M1A, and AKM variants. The rifle of my choice is therefore an AKM type of rifle as it is proven to be the most rugged and reliable. I’ve seen and repaired many rifles and know of some of their weaknesses. IHMO, most lack the training to properly use a military rifle other than an AKM variant. However, an AK-47 style rifle has limitations in terms range, accuracy, energy on target, parts and ammunition availability that the 7.62 NATO rifles provide adequately well.
I will provide some, yet not all the technical differences that sets military spec ammunition apart from its commercial counterpart. These differences are critically important. Military ammunition and its rifles are designed for the rugged conditions of war. Commercial rifles and ammunition are not designed for war or battle rifles. And would it not be safer to err on the side of caution than court a possible disaster?
Unfortunately some have invested in cases of .308 Winchester hunting ammunition that they intend to use in their AR-10 style rifle and no longer have financial means of correcting this error by buying the same quantity of the proper ammunition type when ammunition prices are now much higher. Perhaps this article might provide enough motivation to dig deep and do the research and purchase the correct ammunition before it is nearly impossible to do so at a later date.
Did you know the the Armalite AR-10 has firing pin that is held in place to prevent slam fires, but the LR308 (an AR-10 variant rifle) does not? Commercial .308 Winchester ammunition uses softer primers that could accidentally ignited by a free-floating firing pin setting off the cartridge when the bolt is out of battery (not locked into the chamber). Did you know that the M1 Garand and the M14/M1A has a free-floating firing pin as well? And that firing factory-loaded hunting .30-06 ammunition could quickly bend the operating rod on these rifles? I’ve worked on all these and other rifles. There are many reasons to use the correct mil-spec ammunition and not commercial ammunition in these and other military rifles.
Sadly, within the firearms industry, there remains a persistent state of confusion between the slight yet important differences between ammunition loaded to mil-spec (military specifications) and ammunition intended for consumers, a cartridge that is closely related to 7.62 NATO, yet is potentially dangerous in rifles chambered in 7.62 NATO. The commercial adaption of 7.62 NATO is the .308 Winchester cartridge is a ‘kissing cousin’, yet it should not be used in any rifle chambered for 7.62 NATO.
Because of the popularity of .308 Winchester, it is widely available and is the most common medium bore cartridge designed for hunting big game found in North America. However, because 7.62 NATO is a military cartridge, it would be found in greater supply than the commercial variant. This is important information for preppers and survivalists who will have either or both rifles chambered in these cartridges.
For most survivalists, common caliber cartridges and the rifles that shoot it are the most sensible choices as the purchase price would be lowest and they would be in good supply on the market in the future. As these cartridges would also be the most sought after and likely could be used as alternative currency. Therefore 7.62 NATO and 5.56 NATO, then .308 Winchester, and finally .30-06 that are the most common cartridges in the U.S., are the best choices.
Because all rifles that can fire .308 Winchester can also use 7.62 NATO, and all rifles chambered in .30-06 can fire .30 cal. M1/M2 ball ammunition that is used in the M1 Garand. However, rifles chambered in .223 Remington should not be used to fire 5.56 NATO as the maximum pressures allowed in 5.56 NATO is up to 62,000 psi, while .223 Remington ammunition, and the rifles chambered in .223 Remington should not exceed 51,000 psi. Yes, there are exceptional examples of semi-auto box-fed rifles that can handle both mil-spec ammunition and the commercial variety, but if the owner is uncertain if they own such a rifle, I would not take the risk and use commercial ammunition in that rifle.
JWR Adds: It is noteworthy that several years ago, Ruger switched from .223 Remington to 5.56mm NATO markings on their Mini-14 family of rifles. But they have repeatedly stated that with the exception of the Mini-14 Target Rifle (which accepts only .223 Remington), all other Mini-14s can safely shoot both .223 Remington and 5.56mm NATO.
Military Cartridges Versus Commercial Cartridges
A rifle in .308 Winchester is at the top of list as a hunting rifle and possible counter sniper rifle. Semi-auto box fed battle rifles however should not use .308 Winchester ammunition. If you have such a battle rifle, then you should also have a dedicated hunting rifle chamber specifically for .308 Winchester. If you have a an M1 Garand that is designed to fire .30 caliber M2 or M1 ball ammunition, then one should own a dedicated hunting rifle chambered in .30-06 ammunition that is intended for hunting so that commercial hunting and precision commercially made .30-06 can be used in a bolt action rifle. And the same goes for semi-auto box fed or any rifle chambered in 5.56 NATO, it should not use its commercial variation, .223 Remington.
I say all this up front should the technical differences be not enough impress upon the reader not to use any other ammunition type other than ammunition designed to military specifications in their military type rifles. Do not use .308 Winchester in a rifle chambered in 7.62 NATO, or commercial .30-06 in your M1 Garand, or .223 Remington in a 5.56 NATO rifle. There are many good reasons these military cartridges are designed the way they are so that they will be safe and reliable under battlefield conditions that few civilian shooters have experienced.
In addition, reloaders should take note that there are important differences and seek out the best reloading procedures and military specifications to properly reproduce mil-spec ammunition that may someday be needed to protect lives and liberty. Do not use thinner-walled commercial cases, even if they are properly resized for mil-spec chambers. Always use mil-spec primers and the proper load data and projectile weights for service rifles etc. When reloading for semi-automatic gas operated rifles, use a cartridge comparator to ensure that each round produced is the same in dimension.
7.62 NATO Vs .308 Winchester
Because .308 Winchester is a similar, yet different cartridge, and is a commercial cartridge that can be loaded to very high pressures up to 62,000psi instead of 51,000psi (7.62 NATO).308 Winchester should not be used in any rifle chambered in 7.62 NATO (7.62×51). There is a possibility of a hazardous ammunition mix up that might cause injury to the shooter or render their rifle inoperable.
Not only does 7.62 NATO have slightly shorter case head to neck length (a difference of 0.016 inches shorter), it also has a much thicker case wall that allows it to expand properly in a larger mil-spec chamber and grip the wall of the chamber and to withstand rapid and forceful ejection forces applied by the gas operated bolt at full speed, and when excessive dirt and heat would work to hold the case inside the chamber. Always carry a ‘stuck case’ removal tool with the rifle.
The differences between military specification and SAAMI specifications could potentially cause an excessive headspace condition as well as a stuck cartridge case. The thinner walls of the SAAMI spec case can allow the case head to become torn away from the case leaving a broken case stuck in the chamber. The potential for case head separation in generously sized cartridge chambers of 7.62 NATO battle rifles is greater as military spec chambers are intentionally designed to handle excessive chamber heat and the presence of debris in the chamber as a result of battlefield conditions is a necessary design feature. Consider the extreme heat created by the rapid firing of a semi-auto rifle and that the reduced size of the chamber place more stress on the case head of the cartridge during extraction. In addition, dirt or debris that accumulates in battlefield conditions also contributes to the possibility that the case head could be torn off by the extractor. If we are using commercial cases that are thinner than NATO spec cases then there is a much greater chance the rifle could become inoperable when a broken case is stuck in the chamber.
A Warning to Reloaders
The thinner-wall commercial cases could be stretched too thin in generously sized military chambers and more so after repeated firing. For reloaders, this work hardening of brass once or many times resized makes the cases increasingly brittle adding to the risk of a stuck case or even case head separation. All these factors compound increasing the chance the rifle could become rendered inoperable. I do not advise reloaders to resize once fired commercial .308 Winchester brass or commercially made .308 Winchester ammunition in 7.62 NATO rifles.
Commercial brass is not designed to expand to fill and adequately grip the walls of the larger chambers of 7.62 NATO spec rifles or to withstand the stresses of extraction in a semi-auto gas operated rifle. There are many reasons the 7.62 NATO cartridge is designed for use in battle rifles. Unless the ammunition or case is 7.62 NATO, do not use it in another 7.62 NATO rifle. For example, a modern AR-10 may have tighter chamber than a M1A and your hand loads may not work reliability in another rifle.
For example, the Armalite AR-10 might better tolerate the use of certain, but not all .308 Winchester loads, better than a M1A rifle that can easily be damaged by a out of spec cartridge powder burn rate for the M1A and bend the ‘op rod’ (Operating Rod). The Hogodon Reloading Center provides Service Rifle reloading data that lists the correct cartridge powder types and maximum powder charges that should be adhered to. Some commercial makers of ammunition may advertise that certain of their ammunition is NATO spec, but is it? Be sure and purchase only mil-spec, NATO ball ammunition.
Over-Gassing a Gas-Operated MBR
In addition, the much higher pressures of the .308 cartridge would greatly contribute to the potential of case head separation and over gassing of gas operated rifles. And because a wide variety of powders of greatly different burn rates are used in commercial .308 Winchester loads, these various and non standard pressures for military spec rifles can cause excessive and ill timed peak gas pressures in gas operated battle rifles.
Rifles such as M1A (M14 variant) are particularly vulnerable as the ‘op rod’ (operating rod) is easily damaged, yet even common AR-10 variants such as the LR308 and others, are not designed to handle .308 Winchester ammunition on a consistent basis. In general, sustained use of .308 Winchester in 7.62 NATO gas operated rifles of most models can over time, produce damage to the gas system and the mechanics of any gas operated rifles. If using an M1 Garand, one can install a Shutzer Plug to reduce gas system pressure, or if we have an L1A1, one can adjust up or down the pressure in the gas system, but these are the exceptions. Yet commercial ammunition pressures could still overwhelm these devices’ ability to adapt the rifle to the ammunition.
.308 Winchester Precision Rifles
I would argue that it would advantageous to have a bolt-action precision rifle in .308 Winchester with 24-inch to 26-inch barrel length and with a barrel twist rate of 1:10 as this rifle can take advantage of the high quality commercial and hand loaded ammunition that use full pressure (up to 62,000psi) that result in top velocities with projectiles with extreme high ballistic coefficients. The long barrel provides additional muzzle velocity that further flattens the trajectory and makes efficient use of slower powder needed for heavier projectiles to make long range shots easier. Generally, modern bolt-action .308 Winchester rifles can handle 7.62 NATO. However, shooters should be careful to separate their .308 Winchester ammunition from their 7.62 NATO battle rifle.
Modern .308 Winchester will have an important role to play with the use of bolt action rifles that are more easily accurized than semi-auto rifles. Any modern bolt action would be extremely important in retreat defense and as a much-needed hunting rifle. Long range shots might be needed to take game animals at longer range as these animals might be hunted to near extinction levels during a famine or another and greater economic depression. Most modern hunting rifles with a standard 3×9 scope are accurate enough to be useful in a defense role out to 500 yards if the shooter is skilled and well practiced.
Conclusion: Operators Beware
These facts are mostly unknown to owners of rifles chambered in 7.62 NATO and many owners of rifles chambered in 7.62 NATO that have a significant supply of .308 Winchester, therefore I am compelled to mention this problem given this last opportunity to do so. Or you might be a person who has an M1 Garand and stocked up on commercial .30-06. Do not use commercial .30-06 in the M1, it will, sooner or later, ruin the rifle.
Since the AR-15 is now the most popular military variant rifle, the reader could be heavily invested in commercially made .223 Remington. While chamber pressure of .223 Remington is safe in a rifle chambered in .223 Wylde or 5.56 NATO, the primers and the cases of commercial ammunition make it ill-suited to use in the AR-15 for the same technical reasons that make .308 Winchester unsafe or in appropriate in a gas operated rifle chambered in 7.62 NATO. Perhaps it will tolerate this ammunition in training situations, yet not in actual battlefield conditions. I would not risk it, so I would purchase high quality 5.56 NATO ball ammunition such as M855 for self-defense situations.
If someone is fully invested in .308 Winchester ammunition or other commercial ammunition that they intended for use their NATO spec or other military rifle such as the M1 Garand, it was a wise investment even if we can not use it in our battle rifle. Any common caliber cartridge, especially military ball or mil-spec ammunition could be used as a replacement for money or as a premium commodity in a barter situation.
In a societal collapse, I anticipate that there will be plenty of rifles available, yet not enough ammunition. Frankly, it would be hard to possess too much ammunition, and for battle rifles it would certainly be wise to only use ammunition made specifically for use in military rifles.
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