I maintain that the M16 is garbage. Making that assertion is pretty much the fastest way to get hatemail on the internet, though 
Current issue A4/M4s benefit from a lot of improvements over the original M16s, but they are still woefully inadequate for a rifle I’m supposed to trust my life to. I submit the following for your consideration.
A lot of people give flack to the Army Ordinance Board for changing the powder composition of the rounds back then, but I have to say that they made the best choice available to them. The advanced IMR powder that the M16 was designed to use couldn’t be produced in enough quantity to supply the war effort, even if every batch worked as advertised. The problem was that every other batch failed quality control and had to be discarded. So the AOB went with the same gunpowder that they had been using for decades, which was in ready supply, easy to produce, and, let us not forget, cheaper. That was the root cause of the notorious jams of early production M16s. IMR powder burned more quickly, resulting in a steady increase of pressure early in the firing cycle, with the pressure already reducing as the bullet passed the gas-port. Ball-and-Stick powder built pressure later in the firing cycle, but much more dramatically (if you compare the two on a chart, the IMR pressure resembles a bell curve where the older powder more closely resembled a spike). The problem was that the peak pressure coincided with the point at which the bullet was in the vicinity of the gas port. The hot gasses would travel down the gas tube and cycle the weapon while the cartridge was still obturated, causing the extractor to either skip over the lip, or pull through it. The resulting jam required the use of your cleaning kit to clear. I don’t know that they ever really fixed this timing issue. They chromed to bore to reduce drag between the cartridge and the chamber, which allowed the action to extract the cartridge even while it was obturated, and they added a heavier buffer group to slow down the action. The upshot of this is that modern rifles can accept a wider variety of powders from a number of different manufacturers (more applicable to the civilian shooter than the military one).
There are a lot of myths regarding the M16, none more enduring than the myth of the tumbling bullet. A small number of early production rifles were fielded with a 1/18 twist. This rate was insufficient to stabilize the small projectile, resulting in the bullet turning sideways in flight. The result is similar to the difference between a diver using good form smoothly entering a pool versus a diver that belly flops. A much larger amount of energy was transfered to the target by bullets flying sideways, leading to rave reviews from the field about the amount of damage caused by these tiny bullets (the report about a 5.56 “tearing a man’s arm off” comes to mind). Unfortunately, one of the side effects of this instabity was accuracy that would make Nikolai Kaleshnikov weap. As time went on, twist rates were tightened, untill today, modern M16s are fielded with a 1/7 twist. This provides for a very stable bullet, but, unfortunately, they travel completely through their targets, leaving only a 22 hundredths of an inch hole in their wake, unless they hit bone. There is evidence that if the bullet is traveling between 2200-2700fps when it hits a person, it may fragment, causing catastrophic damage, however this is not a design feature, merely a fluke. Alas, I am told that this only occurs a fraction of the time, and can only happen inside of approximately 125yds from an M16, or 15yds from an M4.
As for the notorious direct impingement (DI), it has its strengths, as well as weaknesses. Mainly, it has two problems that concern the user. Firstly, it causes the action to heat up more than a piston would. There are various opinions about how serious this is, but in my opinion, it’s preventable. After even a single magazine, the receiver is noticably warm. In intense firefights, it can result in the rifle overheating and breaking down sooner than a piston system might. Some accuse the users that point this out of lacking fire discipline, but that’s a concept that tends to be forgotten when you’re receiving effective small arms fire. Never mind that one of the big selling points of the M16 was that it could generate such a large volume of small caliber fire. Secondly, the carbon that pollutes the action makes it a devil to clean, and, considering that the design cannot tolerate particulate contamination of the action (addressed below), may be considered this rifle’s achilles tendon. For the logisticians consideration, that same heat-and-carbon combination increases life-cycle costs, and reduces the overall life of the weapon. On the other hand, DI does have some benefits. It reduces the number of moving parts, and reduces weight. More important than that it reduces weight, is where it reduces weight, namely, near the nose of the rifle, where it must be supported at arm’s reach. Another infrequently considered bonus to DI systems is that it does not require a firm mounting point on the barrel, meaning that rifles using this system may have their barrels free-floated, increasing accuracy. The DI system also reduces the amount of mass moving out-of-line with the bore, making the rifle easier to keep on target during rapid or auto fire.
Another point for concern is the magazine. Let us be realistic, magazines are the weak point in any auto-loading design. Though I lack familiarity with the AK series rifle, I’d wager a month’s salary that a bad magazine could cause even that leviathan to falter. When the M16 was new issue, it was originally intended for the magazines to be disposable. However, given that long-term storage of cartridges in their magazines will result in deformed feed lips and followers, as well as weak magazine springs, this proved impractical. The older system of long-term storage (stripper clips, bandoliers, and water-proof boxes) prevailed, with the addition of a speed-loader in each bandolier of ammunition. However, the design and manufacture of magazines was not changed. As a result, modern USGI magazines are notorious for spontaneous failure (from time to time belching their full load of rounds in a humorous variant of 52-card pickup). Most of the time this failure announces itself in the form of double feeds, which may sometimes be ameliorated by grasping the magazine and applying foreward pressure while firing. An attempt was made to develop a go-no-go gauge for the magazines that resulted in failure, as no gauge produced could reliably tell bad magazines from good ones. This concern, at least, has been addressed by the private sector. Users of Magpul magazines swear by them much as an earlier generation swore by the Bible.
Finally, we come to the real problem of this series of rifle. Many people who are unfamiliar with the M16 claim that its internal tolerances are too tight for a battle rifle, that these unspecified “tight tolerances” are the culprit of the M16’s notoriously bad reliability. Such claims are dismissed by people familiar with the rifle, and rightly so. But that doesn’t mean there isn’t a problem. What has historically been attributed to the tolerances of the rifle are more accurately attributed to a poorly designed bolt carrier group (BCG). During counter recoiling, as the bolt attempts to strip a fresh cartridge off of the magazine, the bolt and BCG are compressed between the buffer spring and the cartridge. This compression causes the bolt to try to cam to the shooter’s left (prevented by the bolt pin inserted through the carrier group under the gas key) and the BCG to try to twist to the shooter’s right (prevented by the guides of the receiver). When the rifle is clean, this produces negligable additional resistance. The analogy I like to use is a car with glassed-over brakes. The action is slowed, but not appreciably. With the introduction particulate matter (sand, dirt, carbon, etc), it is analogous to replacing the brakes in the aforementioned automobile. The friction between these bearing surfaces increases dramatically, slowing the BCG down. Even so, I believe that the rifle would still function, were it not for the fact that there are four energy-intensive (relative to the amount of force produced by the buffer spring) actions that need to happen at the end of each cycle. Firstly, the spring loaded extractor must be forced over the lip of the freshly chambered cartridge, while simultaneously compressing the ejector spring. These two springs are fairly stiff. After these two springs are overcome, the bolt must cam into a locked position behind the barrel as the carrier group continues to slide home. Finally, the auto-seer must be reset by the carrier group coming to rest in the battery position. This combination is the reason that the rifle notoriously fails to function when dirty, falsely attributed to tight tolerances. Frankly, as constructed, looser tolerances would likely cause the rifle to fail even when clean. Efforts have been made to partially address this issue. After market rolling-cams have been introduced to replace the OEM pin, but I believe that the true solution will be to somehow prevent the bolt from trying to prematurely cam that is internal to the BCG.
That just about sums up the rifle itself. Never mind the pack of lies, deceit, back stabbing, and all around political chicanery involved in its adoption. I think I would despise these rifles even if they were good just because they will forever be a testament to corrupt politicians destroying careers and national institutions that stand between them and their goals. Each M16 should be etched with the phrase “RIP Springfield Armory” I firmly believe that the M16 has never been the better rifle in any test, only that it was a handy tool to aid McNamara (may he enjoy his time squatting on the coals) in destroying the Springfield Armory.
