Reasons for infantry rifle change

We were issued M-16A1’s when I was in boot camp back in '83. At the time I recall one of the D.I’s remarking how it was “sad that we were reduced to using ‘plastic toy M-16’s’ and it never would have happened had we not needed a lighter weapon to supply our [former] South Vietnamese allies with.” The statement struck me as the usual sort of b.s. you’d expect to hear from a D.I., but perhaps there was a kernel of truth to his claim?

What were the real reasons the US military chose to transition away from the M-14 and adopt the M-16 back in 1970 as the new standard assault rifle? Why the move to a smaller and lighter weapon?

It had nothing at all to do with our South Vietnamese allies, but there is a grain of truth to it. It was all about reducing weight.

The idea is that if you reduce the overall weight of the soldier’s other gear, he can carry more ammo. And if you use smaller and lighter ammo, he can carry more of that, too. Up until then, the standard infantry round tended to pack quite a bit of a punch, so reducing that punch was a bit controversial at the time (and still is). The M-16’s 5.56×45 round isn’t designed to be as hard hitting as the earlier 7.62×51 (basically a tweaked .308). It’s designed to be a smaller and lighter, and “good enough” for infantry use.

Lighter and smaller ammo also means that you can stuff more rounds into an ammo truck, meaning you need fewer ammo trucks. It also means fewer cargo plane loads, etc. The effects go all the way through the supply lines.

Having the best weapon doesn’t win wars (just ask the Germans from WWII). Logistics and producability wins wars.

Yeah, it’s bullshit…as one can see by the fact that it’s still in operational use 23 years after your experience (and originally operational as of 1964 IIRC). There is zero way the US would continue to use the things for so long without replacement (yet) if they weren’t an effective battle rifle.

As to why, well, the weight was certainly part of it. It’s a lot lighter than the M-14 when it was originally developed (it’s also easier and cheaper to manufacture and maintain). Not only the weapon but the ammo (the 5.56 is a lot lighter and you can carry more than the 7.62). Those are very important factors for gun bunnies who have to hump their weapons and ammo through the bush (mind, I was in the Navy so I only know this stuff intellectually :p).

At any rate, the M-16, after some initial teething problems has become probably the second best battle rifle of all time (well, arguably anyway), and will remain in service for at least another 10 years or so. Plans to replace it have been ongoing, but thus far, at least as far as I know, there are no serious plans to get rid of it any time soon for the majority of the US armed forces.

During/after WWII, people noticed that few infantry to infantry engagements went much beyond 300-400 meters. What you’ll often hear someone say about range at this point is: “It’s better to have it and not need it than need it and not have it.” This doesn’t take into account the opportunity cost of having a full power cartridge.

With a medium power round, you can carry about twice as many rounds for the same weight, have more ammo in a magazine/ammo belt, have less felt recoil. This all helps increase the practical rate of fire. A shorter, lighter weapon is also more wieldy.
While all those factors were particularly useful in Vietnamese jungle warfare, the US would have ended up with a medium power caliber anyway. The British had a medium power design shortly after WWII (which wasn’t adopted to conform to the US-imposed 7.62NATO), the Soviets went with the medium power 7.62X39mm circa 1947 and the Germans initiated but didn’t have the time to complete the switch in the latter half of WWII.
That process is still ongoing. Main issue rifles are getting shorter and lighter (before accessories are added on) and PDWs may before widespread at some point.

In WWII, GIs carried 88 rounds for their 30-06 Garands.

Now, they carry 200- 500 rounds.

Here’s a basic history of the standard infantry weapon in the US and the thought that went into it.

Once the US revolutionary war started, for some silly reason the British weren’t willing to give us British muskets any more (gosh, wonder why…). The French however were all too happy to sell us their older muskets. The first weapons made in the US were basically copies of the French Charleville muskets (that shouldn’t actually be called Charlevilles, but that’s a topic for another thread).

In the war of 1812, they found that they couldn’t produce muskets anywhere near fast enough, so a lot of improvements were made that were focused on producability. This trend continued to the mid 1830s. In the 1840s, they switched from smooth bore flintlocks to percussion cap rifle-muskets. In 1855 they tried to replace the caplock with a paper tape cap system kinda like what you have in old toy cap guns, but that didn’t work very well and in 1861 they went back to the old style percussion caps. Percussion cap rifle-muskets were the main weapon of the US Civil War.

As an aside, the Civil War era rifle-musket and its accompanying Minie ball were the worst standard infantry weapon to be shot with in all of history. Those big slugs of lead made huge holes and easily shattered bone.

Anyway, the increased rate of fire from cartridge rifles definitely made an impression on folks during the Civil War, so after that, they converted a lot of the rifle-muskets to cartridge rifles. Google Trapdoor Springfield Rifle if you want more info on those). The Trapdoor Springfields remained the standard infantry rifle up through the 1890s.

The next improvement was to use magazines instead of loading each round one at a time. This was adopted in the Krag-Jorgensen rifle.

In the Spanish-American war, American soldiers got their butts kicked by the German 1893 Mauser rifle. That (along with a lot of politics) led to the design of the Model 1903 Springfield rifle.

The next improvement was to make the weapon semi-automatic, and that became the M1 Garand. That was used extensively in WWII.

The next big improvement was to make the weapon capable of select fire, so that it could fire in semi-automatic mode like the M1 Garand, but could also fire in full auto mode if desired. That became the M-14.

Up until this point, all standard infantry weapons fired a full power round. In the musket era, your typical military musket was somewhere around .50 to .75 cal. (with some higher), where a typical hunting rifle was more like .40 to .50 cal. By the early 1900s, military forces all around the world eventually settled on something around .30 cal. (7.62 mm is .30 inches). The M-14 was the last standard infantry weapon to fire this type of round, at least in the US.

Up until this point, most armies tended to go in the same general direction, design-wise. They all went from flintlocks to caplocks to cartridge rifles to semi-auto to selective fire. But this is where the two largest armies (the US and the USSR) diverged significantly.

The M-16, as already mentioned, was designed to reduce the weight of both the weapon and the ammo.

The Soviets, in contrast, kept the larger 7.62 mm round, giving the AK -47 more of a punch than the M-16. The AK-47 is also cheaper and easier to produce, but its accuracy suffers a bit as a result. The AK-47 is designed to be used within a few hundred yards, for the reasons that MichaelEmouse posted. That’s where most of your infantry battles take place.

The M-16 is better at longer ranges. Hitting a man at 300-400 yards with an AK-47 is going to be mostly a matter of luck, or firing enough lead that something eventually hits. At shorter ranges, the AK-47 is better at punching through thick brush (like the jungles of Vietnam) and can punch through some building walls that will stop an M-16’s lighter round. The tighter tolerances of the M-16 help it to be more accurate, but it’s also easier to foul it up with dirt and stop it from working. The AK-47’s looser fitting parts can take a lot more abuse before anything jams, but they are also one of the main causes of the weapon’s decreased accuracy (and it’s cheaper and easier producability). Guys shooting AKs require more shots (since the weapon isn’t as accurate) and for the same amount of weight, they can’t carry anywhere near as much ammo. Supplying the AK soldiers with ammo also requires more logistics effort all the way up and down the supply chain. Each weapon has its good points and bad points.

The fact that each weapon is very successful proves that either design philosophy works. While they both have their pluses and minuses, neither design has proven itself superior to the point where the other side has chosen to change their design philosophy.

Lately there’s been more of an emphasis on urban combat, and we’re starting to see a lot more bullpup designs as a result. They haven’t replaced the M-16 yet though.

With a shorter case, reducing velocity and power (~1,500 ft-lbs to 2,500 ft-lbs for the 7.62 NATO)

The original M-16(20 in barrel) isn’t far behind the AK in power (1,200-1,300 ft-lbs) though the AK uses a much heavier bullet. (122 gr. vs. 62 gr.)

But Russia HAS changed its design philosophy. The AK-47 was long ago (confusingly) superseded by the AK-74, which fires a 5.45mm round.

From my Dad- a Infantryman in WWII:

And of course, ever since the first 'war" there has been some general, who thought that giving the infantry faster firing weapons would mean they would “waste” ammo. The same type of general who wanted longer, heavier bayonets on rifles. * These generals were never infantrymen.

I’m aware of the AK-74, but I didn’t think that it had completely superseded the AK-47. I could be wrong about that though.

The AK-74M is the battle rifle for the majority of the Russian ground forces. They do still use the AK-47 (well, the AKM) which fires the 7.63x39, just as there are some American forces that still use rifles with the larger caliber, but the 5.56 (5.45 for the Russians) is the most common round these days for general conventional forces.

For some reason I didn’t think that they had adopted it that widely. Thanks for the info.

Small arms fights are generally won by the side that can fire more rounds reasonably effectively. The accuracy if individual rifle fire and “stopping power” of each bullet has a smaller role. If side A with 100 men can fire twice as many rounds as side B with 100 men, the second side will be more effectively suppressed. If 30 guys on side B are keeping their heads down because of the incoming volume of fire, then suddenly it’s 100v70. Then that volume of fire reduces it to 100v50, etc. Once the other side is suppressed you can kill them in all sorts of fun ways. Light rounds mean more rounds per soldier (and higher controllability of automatic fire) and ended up winning out for most types of engagements.

IIRC one of the other reasons for the M16 was it was better-controllable in burst/automatic fire modes. The M14 had much greater recoil and with the barrel axis higher above the butt of the stock, muzzle rise was significant. the barrel of the M16/AR-15 is more or less right in line with the buttstock.

Personally, I wouldn’t call 7.62 x 51 mm NATO ‘full power’. To me, a ‘full power’ round would be the 7.62 x 63 mm (.30-06) or the 7.92 x 57 mm Mauser. IMO, the NATO round is a ‘medium power’ round that just seems like full power because nobody uses the others anymore.

FWIW, I saw a photo in a book sometime in the '80s that showed a pair of photographs of casualties in Vietnam. One photo showed a leg wound from an AK-47/AKM. There was a hole in the calf. The other showed a leg wound from an M-16. The flesh was gone from below the knee to above the ankle. Pretty gruesome, actually.

It’s exactly in line with the top of the buttstock. That’s where the buffer tube and spring is, and where the bolt carrier goes when you fire it. :wink:

I read a book on infantry weapons once upon a time a c, and they talked about this kind of thing. There are a few reasons- among them:

  1. The VAST majority of infantry combat takes place within 300 meters, and most of that is even closer than that. Most casualties outside of this range are caused by crew-served weapons like tripod-mounted machine guns as well.

In WWI, there was an emphasis on full-sized cartridges, such as the .303 British, .30-06 and 8mm Mauser. These rounds were designed to be used in a pre machine gun era when massed rifle fire was the primary way of engaging the enemy, so these cartridges were designed to be effective at absurd distances like 1000 yards, because the infantry tactics employed almost Napoleonic-style volley fire at targets and enemy formations. By the time of WWII these cartridges were pretty much obsolescent, as nobody’s tactics worked that way anymore, but institutional inertia kept the larger rounds in service. Several countries designed and/or introduced intermediate rounds however- the US with the .30 Carbine, the Germans with the 7.92 Kurz and the Soviets with the 7.62x39 (developed in 1943, not in service until 1945)

  1. The 7.62 bullets are bigger and heavier than necessary. All bullets will yaw and tumble, but in gelatin testing, the 7.62 bullets tend to do so deeper than most people are thick. 5.56/5.45 on the other hand, yaw and tumble much earlier, contributing to greater effectiveness at typical infantry combat ranges than their larger brethren.

  2. They’re lighter, so soldiers can carry more.

  3. They’re easier to shoot- firing the big cartridges can be a punishing affair, while the lighter ones are easier to fire.

Likely due to the unstable nature of the round (tumbles in flesh).

Most of the nastiness of the pre-SS109 5.56 rounds actually came from a weak cannulure that would fragment the round if it were going above 2700 fps. From an M16 16" barrel that gives an effective fragmentation range of IIRC around 125m. Less for shorter barrels.

Outside that range, it doesn’t have good terminal ballistic performace, which is to say that it really doesn’t do that much damage.

The newer rounds we use, the SS-109 rounds, with the new twist rate, are poor performers for wounding at any range. The round doesn’t fragment and is far more stable (spinning faster, takes longer to yaw) and basically pokes .22 sized holes in people. It was designed when there was a fear in the 80s that the Soviets would deploy body armor effective against the old 55gr round to be better for armor piercing, but that armor never manifested and now we’re stuck with a bullet that doesn’t do much wounding.

The 5.45 on the other hand creates nasty wounds from an assymetry in the bullet tip that causes it to yaw within 2-3 inches of striking flesh. In the 80s the Afghanis fighting against the USSR named it the “poison bullet” because the wounding pattern often resulted in untreatable lethal wounds.

Much of the often reported jamming issues with the M16 could have been avoided. The initially-issued M16s didn’t come with a cleaning kit. Cannot imagine the thinking behind this. Making a bad situation worse, the Army used a cheaper ammunition with was considerably dirtier than its replacement. Unlike an AK47, whose tolerance are relatively loose, those of a 16 are not. So, when you combine no cleaning kits, dirty ammo and the conditions in VM, it’s no wonder there were problems.