Design M16 rifle

1 design

1.1 barrel
1.2 recoil
1.3 sights
1.4 range , accuracy
1.5 terminal ballistics
1.6 magazines
1.7 muzzle devices
1.8 grenade launchers , shotguns
1.9 riot control launcher
1.10 bayonet
1.11 bipod

design

m16a1 cutaway rifle (top) m16a2 (below)

the m16 lightweight, 5.56 mm, air-cooled, gas-operated, magazine-fed assault rifle, rotating bolt. m16 s receivers made of 7075 aluminum alloy, barrel, bolt, , bolt carrier of steel, , handguards, pistol grip, , buttstock of plastics.

the m16a1 lightweight @ 7.9 pounds (3.6 kg) loaded 30-round magazine. less m14 replaced @ 10.7 pounds (4.9 kg) loaded 20-round magazine. lighter when compared akm s 8.3 pounds (3.8 kg) loaded 30-round magazine.

the m16a2 weighs 8.8 lb (4.0 kg) loaded 30-round magazine, because of adoption of thicker barrel profile. thicker barrel more resistant damage when handled , slower overheat during sustained fire. unlike traditional bull barrel thick entire length, m16a2 s barrel thick forward of handguards. barrel profile under handguards remained same m16a1 compatibility m203 grenade launcher.

barrel

early model m16 barrels had rifling twist of 4 grooves, right hand twist, 1 turn in 14 inches (1:355.6 mm) bore - same rifling used .222 remington sporting round. shown make light .223 remington bullet yaw in flight @ long ranges , replaced. later models had improved rifling 6 grooves, right hand twist, 1 turn in 12 inches (1:304.8 mm) increased accuracy , optimized use standard u.s. m193 cartridge. current models optimized heavier nato ss109 bullet , have 6 grooves, right hand twist, 1 turn in 7 in (1:177.8 mm). weapons designed accept both m193 or ss109 rounds (like civilian market clones) have 6-groove, right hand twist, 1 turn in 9 inches (1:228.6 mm) bore, although 1:8 inches , 1:7 inches twist rates available well.

recoil

(m16 s) stoner system provides symmetric design allows straight line movement of operating components. allows recoil forces drive straight rear. instead of connecting or other mechanical parts driving system, high pressure gas performs function, reducing weight of moving parts , rifle whole. m16 s straight-line recoil design, recoil spring located in stock directly behind action, , serves dual function of operating spring , recoil buffer. stock being in line bore reduces muzzle rise, during automatic fire. because recoil not shift point of aim, faster follow-up shots possible , user fatigue reduced. also, current model m16 flash-suppressors act compensators reduce recoil further.

notes: free recoil mathematical equation calculated using rifle weight, bullet weight, muzzle velocity , charge weight. measured if rifle fired suspended strings, free recoil. mentioned above, rifle s perceived recoil dependent on many other factors not readily quantified.

sights

soldier fires m16a2. note: upper receiver showing carrying handle , rear sight



m16a2 rear sight

the m16 s distinctive ergonomic feature carrying handle , rear sight assembly on top of receiver. by-product of original design, carry handle served protect charging handle. line of sight 2.5 in (63.5 mm) on bore, m16 has inherent parallax problem. @ closer ranges (typically inside 15–20 meters), shooter must compensate aiming high place shots desired. m16 has 500 mm (19.75 inches) sight radius. m16 uses l-type flip, aperture rear sight , adjustable 2 settings, 0 300 meters , 300 400 meters. front sight post adjustable elevation in field. rear sight can adjusted in field windage. sights can adjusted bullet tip or pointed tool, troops trained 0 own rifles. sight picture same m14, m1 garand, m1 carbine , m1917 enfield. m16 has low light level sight system , includes front sight post small glass vial of (glow-in-the-dark) radioactive tritium h3 , larger aperture rear sight. m16 can mount scope on carrying handle. advent of m16a2, new adjustable rear sight added, allowing rear sight dialed in specific range settings between 300 , 800 meters , allow windage adjustments without need of tool or cartridge. modern versions such m16a4 use picatinny rails, allows use of various scopes , sighting devices. current united states army , air force issue m4 carbine comes m68 close combat optic , back-up iron sight. united states marine corps uses acog rifle combat optic , united states navy uses eotech holographic weapon sight.

range , accuracy

the m16 rifle considered accurate . light recoil, high-velocity , flat trajectory allow shooters take head shots out 300 meters. newer m16s use newer m855 cartridge increasing effective range 600 meters. more accurate predecessors , capable of shooting 1–3 inch groups @ 100 yards. in fallujah, [iraq] marines acog-equipped m16a4s created stir taking many head shots until wounds closely examined, observers thought insurgents had been executed. newest m855a1 epr cartridge more accurate , during testing ...has shown that, on average, 95 percent of rounds hit within 8 × 8-inch target @ 600 meters.

note *: effective range of firearm maximum distance @ weapon may expected accurate , achieve desired effect.

note **: horizontal range distance traveled bullet, fired rifle @ height of 1.6 meters , 0° elevation, until bullet hits ground.

note ***: lethal range maximum range of small-arms projectile, while still maintaining minimum energy required put man out of action, believed 15 kilogram-meters (108 ft.-ibs.). equivalent of muzzle energy of .22lr handgun.

note ****: maximum range of small-arms projectile attained @ 30° elevation. maximum range of safety interest, not combat firing.

nato e-type silhouette target



terminal ballistics

the 5.56×45mm cartridge had several advantages on 7.62×51mm nato round used in m14 rifle. enabled each soldier carry more ammunition , easier control during automatic or burst fire. 5.56×45mm nato cartridge can produce massive wounding effects when bullet impacts @ high speed , yaws ( tumbles ) in tissue leading fragmentation , rapid transfer of energy.

the original ammunition m16 55-grain m193 cartridge. when fired 20 barrel @ ranges of 100 meters, thin-jacketed lead-cored round traveled fast enough (above 2900 ft/s) force of striking human body cause round yaw (or tumble) , fragment dozen pieces of various sizes created wounds out of proportion caliber. these wounds devastating many considered m16 inhumane weapon. 5.56mm round s velocity decreases, number of fragments produces. 5.56mm round not fragment @ distances beyond 200 meters or @ velocities below 2500 ft/s, , lethality becomes largely dependent on shot placement.

with development of m16a2, new 62-grain m855 cartridge adopted in 1983. heavier bullet had more energy, , made steel core penetrate soviet body armor. however, caused less fragmentation on impact , reduced effects against targets without armor, both of lessened kinetic energy transfer , wounding ability. soldiers , marines coped through training, requirements shoot vital areas 3 times guarantee killing target.

however, there have been repeated , consistent reports of m855 s inability wound (i.e. fragment) when fired short barreled m4 carbine (even @ close ranges). m4 s 14.5 barrel length reduces muzzle velocity 2900 ft/s. reduced wounding ability 1 reason that, despite army s transition short-barrel m4 s, marine corps has decided continue using m16a4 20″ barrel 5.56×45mm m855 largely dependent upon high velocity in order wound effectively.

in 2003, u.s. army contended lack of lethality of 5.56×45mm more matter of perception fact. shot placement head , chest, target defeated without issue. majority of failures result of hitting target in non-vital areas such extremities. however, minority of failures occurred in spite of multiple hits chest. in 2006, study found 20% of soldiers using m4 carbine wanted more lethality or stopping power. in june 2010, united states army announced began shipping new 5.56mm, lead-free, m855a1 enhanced performance round active combat zones. upgrade designed maximize performance of 5.56×45mm round, extend range, improve accuracy, increase penetration , consistently fragment in soft-tissue when fired not standard length m16s, short-barreled m4 carbines. u.s. army has been impressed new m855a1 epr round re developing 7.62 nato variant.

magazines

vietnam era 20-round magazine (left) , current issue nato stanag 30-round magazine (right)



improved tan colored m16 magazine follower

the m16 s magazine meant lightweight, disposable item. such, made of pressed/stamped aluminum , not designed durable. m16 used 20-round magazine later replaced bent 30-round design. result, magazine follower tends rock or tilt, causing malfunctions. many non-u.s. , commercial magazines have been developed mitigate these shortcomings (e.g., h&k s all-stainless-steel magazine, magpul s polymer p-mag, etc.).

production of 30-round magazine started late 1967 did not replace 20-round magazine till mid 1970s. standard usgi aluminum 30-round m16 magazines weigh 0.24 lb (0.11 kg) empty , 7.1 inches (18 cm) long. newer plastic magazines half inch longer. newer steel magazines 0.5 inch longer , 4 ounces heavier. m16 s magazine has become unofficial nato stanag magazine , used many western nations, in numerous weapon systems.

in 2009, u.s. military began fielding improved magazine identified tan-colored follower. new follower incorporates extended rear leg , modified bullet protrusion improved round stacking , orientation. self-leveling/anti-tilt follower minimizes jamming while wider spring coil profile creates force distribution. performance gains have not added weight or cost magazines.

in july 2016, u.s. army introduced improvement, new enhanced performance magazine, says result in 300% increase in reliability in m4 carbine. developed united states army armament research, development , engineering center , army research laboratory in 2013, tan colored blue follower distinguish earlier, incompatible magazines.

muzzle devices

bullet exiting a2-style flash suppressor

most m16 rifles have barrel threaded in 1⁄2-28 threads incorporate use of muzzle device such flash suppressor or sound suppressor. initial flash suppressor design had 3 tines or prongs , designed preserve shooter s night vision disrupting flash. unfortunately prone breakage , getting entangled in vegetation. design later changed close end avoid , became known a1 or bird cage flash suppressor on m16a1. on m16a2 version of rifle, bottom port closed reduce muzzle climb , prevent dust rising when rifle fired in prone position. these reasons, u.s. military declared a2 flash suppressor compensator or muzzle brake; more commonly known gi or a2 flash suppressor.

the m16 s vortex flash hider weighs 3 ounces, 2.25 inches long, , not require lock washer attach barrel. developed in 1984, , 1 of earliest privately designed muzzle devices. u.s. military uses vortex flash hider on m4 carbines , m16 rifles. version of vortex has been adopted canadian military colt canada c8 cqb rifle. other flash suppressors developed m16 include phantom flash suppressor yankee hill machine (yhm) , kx-3 noveske rifleworks.

the threaded barrel allows sound suppressors same thread pattern installed directly barrel; can result in complications such being unable remove suppressor barrel due repeated firing on full auto or three-round burst. number of suppressor manufacturers have designed direct-connect sound suppressors can installed on existing m16 s flash suppressor opposed using barrel s threads.

grenade launchers , shotguns

loading m203 40 mm grenade launcher attached m16 rifle practice round.

all current m16 type rifles can mount under-barrel 40 mm grenade-launchers, such m203 , m320. both use same 40 mm grenades older, stand-alone m79 grenade launcher. m16 can mount under-barrel 12 gauge shotguns such kac masterkey or m26 modular accessory shotgun system.

riot control launcher

m234 riot control launcher



usmc m16a2s okc-3s bayonet.

the m234 riot control launcher m16-series rifle attachment firing m755 blank round. m234 mounts on muzzle, bayonet lug , front sight post of m16. fires either m734 64 mm kinetic riot control or m742 64 mm csi riot control ring airfoil projectiles. latter produces 4 5 foot tear gas cloud on impact. main advantage using ring airfoil projectiles design not allow them thrown rioters real effect. m234 no longer used united states forces. has been replaced m203 40mm grenade launcher , nonlethal ammunition.

bayonet

the m16 44.25 inches (1124mm) long m7 bayonet attached. m7 bayonet based on earlier designs such m4, m5, & m6 bayonets, of direct descendants of m3 fighting knife , have spear-point blade half sharpened secondary edge. newer m9 bayonet has clip-point blade saw teeth along spine, , can used multi-purpose knife , wire-cutter when combined scabbard. current usmc okc-3s bayonet bears resemblance marines iconic ka-bar fighting knife serrations near handle.

bipod

for use ad-hoc automatic rifle, m16 , m16a1 equipped xm3 bipod, later standardized bipod, m3 (1966) , rifle bipod m3 (1983). weighing 0.6 lbs, simple , non-adjustable bipod clamped unto barrel of rifle allow supported fire.

the m3 bipod continues referenced in @ least 1 official manual late 1985, stated 1 of stable firing positions prone biped [sic] supported automatic fire.