Lightweight rifle, cal 5.56mm.
Originally in service with the British Army in Malaya as the AR15, it was then adopted as the M16 by the USAF. It was type accepted by USMC and US Army after few modifications had been added, the most notable being the forward assist plunger.
Designed by Eugene Stoner, manufactured by Colt and later FN. Never manufactured by Mattel, contrary to popular belief.
Rotating bolt, considered a 'dirty' weapon because of the direct application of the gas to the bolt without the use of a piston, i.e. it shits where it eats. Originally designed to be a .223 Remington calibre, it was re-designed to take the NATO standard loadings, which are a slightly higher pressure although of practically identical dimensions (in practice, there is no difference between .223 Remington and 5.56 NATO, the difference being in the permitted cartridge overall length and permitted maximum pressure, and certainly no redesign took place for the nominal change - Stoaty)
Upon initial service entry, it attained a reputation for unreliability. This wasn't the fault of the design as much as the fault of the Army trying to cut costs by using a lower grade and dirtier propellant, and also myths such as 'The M-16 never needs cleaning.' The original 'waffle iron' magazines also contributed to the reliability problems. Eventually these problems were rectified.
The M16 and M-16A1 had smooth triangular handguards, (constructed in left and right hand halves,) and was select-fire between semi-auto and full auto using a three-position safety/selector switch, manipulated with the firer's thumb. The M16A2 incorporated a number of changes:
- New flash hider without slots on the bottom to reduce signature by dust or sand being blasted up on firing.
- New foresight blade, (five positions per rotation,)
- New bbl which is thicker in the visible section beyond the handguards and has faster one in seven twist to stabilise the M855 projectile. (As opposed to the earlier one in twelve for the M193 rd.) The bbl retained the original outside diameter under the handguards both to keep weight/cost down and so that the M203 clips cound still be used.
- The round profile handguards are ribbed and now fit above and below the bbl. The upper and lower halves are identical, thus reducing Log Sp.
- The rearsight was changed so that the firer can adjust both windage and elevation from this point, and also do it by hand as opposed to using a tool or bullet.
- A case deflector was added so that when firing from the left shouder the hot brass doesn't scoot down the firer's collar.
- The new pistol grip incorporates a groove for the Sunday-go-courting finger, and has vertical ribs down the backstrap. (No, not for extra pleasure.)
- The full auto capability was replaced by a three rd burst facility to enhance hit probability and conserve ammunition. Unfortunately the rotary sear allows one or two rds only to be fired if the user releases the trigger before the burst has finished. This means that the next time a shot is taked the trigger pressure will be different - not conducive to good marksmanship.
- The buttstock is slightly longer and the buttplate now hatched over the entire surface.
The latest magazines now have a larger anti-tilt follower, and this is also being retro-fitted to older mags.
The latest full-sized M-16 is the A4 variant, with the rear iron sight mounted on a picatinny rail so that it may be quickly replaced with an optical sight.
The carbine version is the M-4, with a telescoping stock and shorter barrel with a distinctive provile where the forward 203 clip can be fitted.
The two major advantages of the rifle are the magazine change and adaptability. 1. The magazine is dropped free with the trigger finger, the replacement mag is inserted without any more manipulation and the bolt released with a slap. 2. The easily-replaced handguards can have up to four mounting rails in addition to any on the top of the body. Many American soldiers have been known to place personally-owned items on their rifles, from Surefire lights and holographic sights through to the issued night vision devices or infra-red pointers.
The 5.56mm round is questioned by some in American circles because of a stated lack of immediate lethal effect. This may be a reflection on the lower muzzle velocity imparted by the shorter carbine which is in increasingly greater circles.
Due to the inline layout all the AR15/M16 family are very controllable in full auto, any perceived problems are always attributable to incorrect firing positions. Those with shorter bbls exhibit more pronounced muzzle blast, but this is common to all short bbl rifles.
More to follow.