The Evolution of the 20th Century American Service Rifle
The United States entered into the 20th century with two service rifles that had served in the Spanish-American war, the M1898 Krag-Jorgensen and the lesser known M1895 Navy Lee. Both had served well, but the small caliber (6mm) and limited usage of the Lee by US naval forces precluded it's use by the Army while the Krag's method of loading was found to be inferior to that of the Mausers used by Spain. Also, the .30-40 round used by the Krag was relatively weak, creating a need for a stronger rifle capable of handling higher pressures. A combination of these factors and others led to the design of the 1903 Springfield rifle.
The 1903 was basically a modified Mauser design, utilizing the same clip loading system and having a similar means of operation. In fact, royalties were paid to Mauserwerke until the onset of WWI. It fired a .30 caliber ball round (.30-06) that was an improvement on the earlier .30-03. All weapons already produced were modified to fire the newer round. This weapon remained the official US service rifle until 1936. However, in the interim there was another rifle in use. When the US saw that it's entry into the Great War was inevitable, it realized that the small number of 1903's would be insufficient for the American Army. The British already had an easily produced serviceable design in the P14 so the US rechambered this weapon and adopted it as the Model 1917. The M1917 was used in much greater numbers than the M1903 during the war but declared surplus afterward and never officially replaced the M1903. A later improvement of the Springfield, the M1903A3, soldiered on into WWII where it took part in some of the early fighting in the Pacific, being preferred over the M1 Garand by the Marines. In it's M1903A4 configuration, the Springfield was used throughout WWII as a sniper rifle. Not a bad track record considering it had been officially replaced almost ten years earlier by the M1 Garand.
In 1936, the United States Army adopted the first general issue semi-automatic battle rifle. Using a Mannlicher-style 8 round en-bloc clip and capable of firing as fast as one could pull the trigger, the M1 Garand was much superior to the 5-shot bolt action Mausers, Arisakas and Carcanos used by the Axis powers. Though not without it's faults (a Garand could not be "topped off" with ammo and allowed Soldiers to expend much more ammunition in combat), the M1 in the hands of the G.I. helped win the Second World War. However, by the end of the war other nations had developed or begun developing a new breed of service rifle. The Germans had designed the predecessor to the StG44 in late 1942. The Soviets would begin production of the legendary Avtomat Kalashnikov 1947 within two years. This new breed of rifle would come to be known by the English translation of Sturmgewehr, Assault Rifle. The Garand was starting to show it's age by the time the Korean conflict ended. The SKS rifles used by some Communist Chinese troops were more reliable in the extreme winter conditions and allowed much more ammunition to be carried by the individual Rifleman. Nonetheless the M1 was not replaced until 1957, by which time most other countries had already adopted an intermediate caliber select-fire battle rifle. It's replacement was the M14.
The M14 was adopted in 1957 and was basically an improved Garand with a detachable magazine and select-fire capability. It was chambered for the 7.62 NATO round which the US had pressured NATO into adopting as a way to keep a full power cartridge standard for US forces. The select-fire option was soon found to be impractical as it made the weapon nearly uncontrollable when fired on full-auto. The M14 was as good a weapon as the other two major 7.62 NATO rifles of the day, the German G3 and Belgian FAL. However, a number of circumstances led to those two weapons being adopted by most free Western nations during the Cold War, while the M14 saw limited use outside of the US. Still, the M14 served well in the early years of the Vietnam conflict. It's superior range was often negated by the terrain, though, and it lacked the rate of fire of the AK47's carried by the North Vietnamese and Viet Cong. In addition, it's size and weight and the weight of it's ammo was not ideal for the humid and unforgiving climate of the Republic of Vietnam. It is making a comeback in the hands of company level designated marksmen in the current war in Iraq. As the last of the full power battle rifles in US service, the M14 continues to do it's job well. Unfortunately, it's potential was not reached during it's tenure as an American service rifle. The end of an era had come as the M14 was the last classic wood stocked service rifle used and the last to be produced at the government Springfield Arsenal (as well as multiple contractors). The era of the M16 series had arrived.
Adopted by the US Air Force in 1964 for use by security personnel, the M16 was modified and adopted by the Army in 1967 as the M16A1. Firing the lightweight M193 5.56 ball round, and capable of firing full-auto or semiautomatic, the M16A1 was more than a match for the twenty year old AK47. There were just a few bugs to be worked out, though. For one thing, the propellant was changed in between testing and production. This created more fouling than intended and gave the M16A1 a certain notoriety. Add this to the fact that no cleaning kits were originally issued with the weapons and multiply it by the fact that many troops in 1967 had only trained with the M14 prior to receiving their unproven new "plastic" rifles in a combat zone and you have a recipe for disaster. A quick remedy was produced in the form of proper training and cleaning kits and by the end of 1967 the weapon was as reliable as any. Regardless, many vets still hold some disregard for the M16. In the 1970's NATO adopted the 5.56 as standard, selecting a different round than that used by the M16A1. In order to get the most potential from this new round (adopted by the US as M855 Ball), the US modified the M16A1, adding a heavier barrel with a different rate of twist, improving the rear sight and replacing the full-auto with a three round burst. This new weapon was designated the M16A2 and adopted in 1982. It has been the basic standard for US troops since that time, though the M16A1 served with some units until the Gulf War. The M16A3 was put into very limited usage in the early 1990's and differs only in it's addition of full-auto to the standard A2 design. The M16A4 differs from the A2 only in the addition of a sight rail where the carrying handle/rear sight used to be. A detachable carrying handle is standard with the A4 though it is usually replaced by some form of optic. The M4 and M4A1 are carbine versions, with the M4 rapidly replacing the M16A2/A4 as the US service rifle. These are much improved over the Vietnam era XM177 carbine that, while used whenever possible, was never officially adopted. Today's M4 is a far cry from the M16A1 of Vietnam. Eugene Stoner's original plan for a family of weapons did not come to fruition as he foresaw it. However, the M16A4 and M4 of today is a modular weapon system capable of using multiple sights, infrared lasers and other add-ons. As one of the longest serving American rifle designs (40+ years), the M16 series will continue to serve in the hands of the American Infantryman for the foreseeable future.
As you can see, the US entered the 20th Century with quality rifles that were inferior to some other weapons of the day. Over the course of the century, we have run the gamut from cutting edge technology (the M1 Garand) to misguided efforts (the M14 and initial adoption of the M16). We finished up strong going into the 21st century with a weapon system that, while over thirty years old, is equal to that carried by any other Army. The US service rifle will continue to evolve on the streets of Iraq and we can only guess at what may come next. The Army is steadily testing new designs but has yet to find one that matches the combat effectiveness of the M16.
I have typed this mostly from previous knowledge, though I had to refer to a couple of sources to confirm a few details. Hopefully everyone learns something from it. If you want more details about a particular rifle, I will be glad to give them when I have the time.
My primary source for confirmation of facts was Wikipedia. My primary source for the bulk of the information was years of interest in surplus firearms and history as well as maintaining and accounting for numerous military small arms over the years.
