AR15 A1, A2, A3, A4
09-16-2008, 09:24 PM
#2
Site Bouncer
Join Date: Dec 2004
Location: Illinois
Posts: 4,099
RE: AR15 A1, A2, A3, A4
Instead of typing a lengthy response, I'll just cut and paste......
Here you go bud:
A1/C7
[/align]
[/align]This is a Bushmaster A1 type upper. It has a tear drop shaped forward assist, and a rear sight that only adjusts for windage (the aperture has two holes the same size one for long distance @375M, the other for a 250M battle sight zero). To adjust the rear sight you either need a rear sight tool, or use a cartridge to press the locking detent. On a 20" barrel each click of windage is 1" at 100 yards. This photo is really of a Canadian C7 type upper (improved A1) it differes from a standard A1 by adding the brass deflector just aft of the forward assist. Early M16s & SP1s used a similar upper (sans brass deflector & forward assist).
[/align]
[/align]A1 type front sights are round and have 5 clicks per rotation (for a 1" change per click at 100 yards when used on a 20" barrel). You don't see these anymore - current rifles produced with A1 type uppers often use A2 type front sights.
[/align]
[/align]A2
[/align]
[/align]This is probably the most common upper seen today. It is used by the M16A2 (and M16A3) and the early version of the M4 carbine. It was the first to have the built in brass deflector. It also sports a round forward assist, and a rear sight that is adjustable for windage and elevation. The elevation wheel is calibrated for M855 shooting out of a 20" barrel out to 800M. On a 20" barrel each click of windage is0.5" at 100 yards, each click of elevation is 1" at 100 yards.There is a large aperture for low light/close in (< 200M) shooting and a small aperture used for longer range shooting (300m+).
[/align]
[/align]A2 type front sights are square and have 4 clicks per rotation (for a 1.25" change per click at 100 yards when used on a 20" barrel).
[/align]
[/align]A3/A4
[/align] removable carry handle
[/align]Also known as the 'flattop'. This is referred to as an A3 type upper by most civilian AR-15 manufactures, and an A4 type by a few. This upper has the same brass deflector and round forward assist of the A2 type upper, but sports a rail to mount optics instead of a rear sight. There is a detachable version of the A2 handle that can be mounted on the rail; its difference is its only calibrated to 600M and the elevation adjustments at 0.5" per click at 100yards. This rail makes it easy to attach a wide variety of optics and night vision so they are at the proper height for a good cheek weld, and they can be removed and reattached with no loss of zero.
[/align]
[/align]Rifle Types:
[/align]
[/align]XM16: Original, non lined barrel, no forward assist. Sights are the windage adjustable only type for the rear, round type front sight. Triangular handguards. Buttstock is 9 7/8" long, has no trapdoor, and the rear sling swivel actually swivels fore and aft. Barrel is light weight (.600" for the whole length) 20" long with an open 3 pronged flash supressor, and 1:12 twist. Selector is safe-semi-auto. Bolt and bolt carrier are chrome plated.
XM16E1: Like the XM16 except forward assist is added to insure bolt closure upon loading.
M16 and M16A1: Essentially the XM16 and XM16E1 with a few mods were officially adopted as the M16 and M16A1. Like above with: Chrome chamber (only, later chrome bore), flash suppressor is changed to the 'bird cage' style to prevent snagging on foliage, bolt carrier is now phosphate covered and chrome lined for reliability. A trap door is added to the stock (to store the cleaning kit), and the rear sling swivel is now fixed in position. Retains the triangular handguards, and XM16 type front & rear sights. A partial magazine fence (raised area) is added to protect the magazine release button on the lower receiver. Selector remains safe-semi-auto.
LTC Santose noted his units M16E1s were updated to partial M16A1 spec (replaced bolt carriers & flash suppressors) in the fall of 1968 in the field (Vietnam). M16 was USAF issue only. XM rifles going thru depot rebuild received all M mods.
[/align]M16A2: Barrel is made heavier forward of the front sight (from .60" to .73" diameter), twist is tightened to 1:7 to handle M855 & M856. Upper is changed to the A2 type (with a fully adjustable rear sight & brass deflector), front sight is changed to a square post with courser adjustments. All plastic parts are made from an improved & strenghthened plastic. Stock is lengthened to 10.5" and the buttplate is checkered to hold it in place better. Pistol grip is thickened and a finger groove is added. Handguards are now changed to the round type (stronger & interchangable). Flash suppressor has the holes on the 6 o'clock position filled in so it also acts like a compensator (and stops kicking up dust when firing from the prone). There are re-enforcements to the lower receiver around the receiver extension and the forward take down pin. Selector is safe-semi-burst (shoots only 3 rounds per press of the trigger).
[/align]
[/align]M16A3: Identical to the M16A2 except selector is safe-semi-auto.
[/align]
[/align]M16A4: Flattop version of the M16A2 (no rear sight - it has the optics rail).
[/align]
[/align]XM177/XM177E1: Submachine gun version of the XM16 (no forward assist USAF GAU-5), or XM16E1 (USA). Round handguards, no bayonet lug, 10" barrel, 4" flash/noise supressor, and a ruber covered aluminum 2 position telescoping stock. Very limited production for special operations forces.
[/align]
[/align]XM177E2: Improved XM177E1 submachine gun.. Has an 11.5" barrel (to mount theXM203 grenade launcher) with the same flash/noise supressor as the XM177E1). Otherwise identical to the XM177E1. Retained the rubber covered aluminum telescopting stock. These were originally issued with what proved to be highly unreliable 30 round magazines (different design than current magazine). There were less than 600 of these submachine guns produced and all were made in 1968. These remained experimental submachine guns and were never adopted, hence the XM model numbers. These were also pieced and parted together at unit level in almost infinite varieties. They retained all XM16 internal parts including the chrome bolt carrier group. The Air Force also used this carbine without the forward assist, its nomenclature was GAU-5/A/A.
[/align]
M4: Early version sported an A2 carry handle, later ones had the flattop receiver. Selector is safe-semi-burst, it sports a 14.5" barrel with an A2 type flash suppressor. Barrel is skinny under the handguards and thickens to .73" from the muzzle to the front sight, there is a cut in the barrel forward of the front sight to facilitate adding a M203 grenade launcher. The stock is of the fiberlite telescoping kind (which has recently been improved). There are also fatteroval profile handguards with double heat shields.
[/align]
[/align]M4A1: Just like the M4, except they are all flattop receivers. Selector is safe-semi-auto. Newer versions have a slightly heavier barrel (thicker under the handguards) to handle full-auto fire for longer periods.
[/align]
[/align]Foreign Versions of the M16 series:
[/align]
[/align]C7: Uses the C7 upper receiver (M16A1 type with brass deflector). Barrel is identical to the M16A2. Handguards and pistol grip are M16A2 style. Buttstock is M16A2 length, but could be optionally ordered as A1 length (CS marked stocks). Canadians also had shims which allowed the stock to be lengthened. Selector is safe-semi-auto.
[/align]
[/align]C7A1: Flattop version of the C7. Popular optic is the Elcan telescopic sight. There is a detachable A1 type (iron) sight that is available (but is made of plastic).
[/align]
[/align]C8: A duplicate of our early version M4 with the C7 type upper,full-auto instead of burst, also the barrel is a thin 'pencil' barrel like the M16A1 (its notheavy in front of sight with a notch like our M4s).
[/align]
[/align]C8A1: A C8 with a flattop upper instead of the C7 upper.
[/align]
[/align]C8A2: At just like the US's M4A1 but the notch in the barrel isn't cut as deep (so a spacer isn't required when using the KAC M203 quick detach mount).
[/align]
[/align]C8LE: a C8A1 where the barrel is .750 from chamber to muzzle (medium weight).
[/align]
[/align]
Here you go bud:
A1/C7
[/align]
[/align]This is a Bushmaster A1 type upper. It has a tear drop shaped forward assist, and a rear sight that only adjusts for windage (the aperture has two holes the same size one for long distance @375M, the other for a 250M battle sight zero). To adjust the rear sight you either need a rear sight tool, or use a cartridge to press the locking detent. On a 20" barrel each click of windage is 1" at 100 yards. This photo is really of a Canadian C7 type upper (improved A1) it differes from a standard A1 by adding the brass deflector just aft of the forward assist. Early M16s & SP1s used a similar upper (sans brass deflector & forward assist).
[/align]
[/align]A1 type front sights are round and have 5 clicks per rotation (for a 1" change per click at 100 yards when used on a 20" barrel). You don't see these anymore - current rifles produced with A1 type uppers often use A2 type front sights.
[/align]
[/align]A2
[/align]
[/align]This is probably the most common upper seen today. It is used by the M16A2 (and M16A3) and the early version of the M4 carbine. It was the first to have the built in brass deflector. It also sports a round forward assist, and a rear sight that is adjustable for windage and elevation. The elevation wheel is calibrated for M855 shooting out of a 20" barrel out to 800M. On a 20" barrel each click of windage is0.5" at 100 yards, each click of elevation is 1" at 100 yards.There is a large aperture for low light/close in (< 200M) shooting and a small aperture used for longer range shooting (300m+).
[/align]
[/align]A2 type front sights are square and have 4 clicks per rotation (for a 1.25" change per click at 100 yards when used on a 20" barrel).
[/align]
[/align]A3/A4
[/align] removable carry handle
[/align]Also known as the 'flattop'. This is referred to as an A3 type upper by most civilian AR-15 manufactures, and an A4 type by a few. This upper has the same brass deflector and round forward assist of the A2 type upper, but sports a rail to mount optics instead of a rear sight. There is a detachable version of the A2 handle that can be mounted on the rail; its difference is its only calibrated to 600M and the elevation adjustments at 0.5" per click at 100yards. This rail makes it easy to attach a wide variety of optics and night vision so they are at the proper height for a good cheek weld, and they can be removed and reattached with no loss of zero.
[/align]
[/align]Rifle Types:
[/align]
[/align]XM16: Original, non lined barrel, no forward assist. Sights are the windage adjustable only type for the rear, round type front sight. Triangular handguards. Buttstock is 9 7/8" long, has no trapdoor, and the rear sling swivel actually swivels fore and aft. Barrel is light weight (.600" for the whole length) 20" long with an open 3 pronged flash supressor, and 1:12 twist. Selector is safe-semi-auto. Bolt and bolt carrier are chrome plated.
XM16E1: Like the XM16 except forward assist is added to insure bolt closure upon loading.
M16 and M16A1: Essentially the XM16 and XM16E1 with a few mods were officially adopted as the M16 and M16A1. Like above with: Chrome chamber (only, later chrome bore), flash suppressor is changed to the 'bird cage' style to prevent snagging on foliage, bolt carrier is now phosphate covered and chrome lined for reliability. A trap door is added to the stock (to store the cleaning kit), and the rear sling swivel is now fixed in position. Retains the triangular handguards, and XM16 type front & rear sights. A partial magazine fence (raised area) is added to protect the magazine release button on the lower receiver. Selector remains safe-semi-auto.
LTC Santose noted his units M16E1s were updated to partial M16A1 spec (replaced bolt carriers & flash suppressors) in the fall of 1968 in the field (Vietnam). M16 was USAF issue only. XM rifles going thru depot rebuild received all M mods.
[/align]M16A2: Barrel is made heavier forward of the front sight (from .60" to .73" diameter), twist is tightened to 1:7 to handle M855 & M856. Upper is changed to the A2 type (with a fully adjustable rear sight & brass deflector), front sight is changed to a square post with courser adjustments. All plastic parts are made from an improved & strenghthened plastic. Stock is lengthened to 10.5" and the buttplate is checkered to hold it in place better. Pistol grip is thickened and a finger groove is added. Handguards are now changed to the round type (stronger & interchangable). Flash suppressor has the holes on the 6 o'clock position filled in so it also acts like a compensator (and stops kicking up dust when firing from the prone). There are re-enforcements to the lower receiver around the receiver extension and the forward take down pin. Selector is safe-semi-burst (shoots only 3 rounds per press of the trigger).
[/align]
[/align]M16A3: Identical to the M16A2 except selector is safe-semi-auto.
[/align]
[/align]M16A4: Flattop version of the M16A2 (no rear sight - it has the optics rail).
[/align]
[/align]XM177/XM177E1: Submachine gun version of the XM16 (no forward assist USAF GAU-5), or XM16E1 (USA). Round handguards, no bayonet lug, 10" barrel, 4" flash/noise supressor, and a ruber covered aluminum 2 position telescoping stock. Very limited production for special operations forces.
[/align]
[/align]XM177E2: Improved XM177E1 submachine gun.. Has an 11.5" barrel (to mount theXM203 grenade launcher) with the same flash/noise supressor as the XM177E1). Otherwise identical to the XM177E1. Retained the rubber covered aluminum telescopting stock. These were originally issued with what proved to be highly unreliable 30 round magazines (different design than current magazine). There were less than 600 of these submachine guns produced and all were made in 1968. These remained experimental submachine guns and were never adopted, hence the XM model numbers. These were also pieced and parted together at unit level in almost infinite varieties. They retained all XM16 internal parts including the chrome bolt carrier group. The Air Force also used this carbine without the forward assist, its nomenclature was GAU-5/A/A.
[/align]
M4: Early version sported an A2 carry handle, later ones had the flattop receiver. Selector is safe-semi-burst, it sports a 14.5" barrel with an A2 type flash suppressor. Barrel is skinny under the handguards and thickens to .73" from the muzzle to the front sight, there is a cut in the barrel forward of the front sight to facilitate adding a M203 grenade launcher. The stock is of the fiberlite telescoping kind (which has recently been improved). There are also fatteroval profile handguards with double heat shields.
[/align]
[/align]M4A1: Just like the M4, except they are all flattop receivers. Selector is safe-semi-auto. Newer versions have a slightly heavier barrel (thicker under the handguards) to handle full-auto fire for longer periods.
[/align]
[/align]Foreign Versions of the M16 series:
[/align]
[/align]C7: Uses the C7 upper receiver (M16A1 type with brass deflector). Barrel is identical to the M16A2. Handguards and pistol grip are M16A2 style. Buttstock is M16A2 length, but could be optionally ordered as A1 length (CS marked stocks). Canadians also had shims which allowed the stock to be lengthened. Selector is safe-semi-auto.
[/align]
[/align]C7A1: Flattop version of the C7. Popular optic is the Elcan telescopic sight. There is a detachable A1 type (iron) sight that is available (but is made of plastic).
[/align]
[/align]C8: A duplicate of our early version M4 with the C7 type upper,full-auto instead of burst, also the barrel is a thin 'pencil' barrel like the M16A1 (its notheavy in front of sight with a notch like our M4s).
[/align]
[/align]C8A1: A C8 with a flattop upper instead of the C7 upper.
[/align]
[/align]C8A2: At just like the US's M4A1 but the notch in the barrel isn't cut as deep (so a spacer isn't required when using the KAC M203 quick detach mount).
[/align]
[/align]C8LE: a C8A1 where the barrel is .750 from chamber to muzzle (medium weight).
[/align]
[/align]
09-16-2008, 09:30 PM
#3
Site Bouncer
Join Date: Dec 2004
Location: Illinois
Posts: 4,099
RE: AR15 A1, A2, A3, A4
I couldn't get the photos to post so here is the link to the web page. There you can see the different receivers of the different models.
http://groups.msn.com/TheMarylandAR15ShootersSite/whatisana1a2a3ora4.msnw
http://groups.msn.com/TheMarylandAR15ShootersSite/whatisana1a2a3ora4.msnw
