Barrett M82 Anti-material rifle,United States of America

The M82 is a short recoil semi-automatic firearm. When the gun is fired, the barrel initially recoils for a short distance (about 1 in or 25 mm), while being securely locked by the rotating bolt. After the short travel, a post on the bolt engaged in the curved cam track in the receiver turns the bolt to unlock it from the barrel. As soon as the bolt unlocks, the accelerator arm strikes it back, transferring part of the recoil energy of the barrel to the bolt to achieve reliable cycling. Then the barrel is stopped and the bolt continues back, to extract and eject a spent case.
On its return stroke, the bolt strips the fresh cartridge from the box magazine and feeds it into the chamber and finally locks itself to the barrel. The striker is also cocked on the return stroke of the bolt. The gun is fed from a large detachable box magazine holding up to 10 rounds, although a rare 12-round magazine was developed for use during Operation Desert Storm in 1991.

The receiver is made from two parts (upper and lower), stamped from sheet steel and connected by cross-pins. The heavy barrel is fluted to improve heat dissipation and save weight, and fitted with a large and effective reactive muzzle brake. On the earlier models the muzzle brakes had a round cross-section; later M82 rifles are equipped with two-chamber brakes of rectangular cross-section.

M82A1 rifles are fitted with scope mount and folding backup iron sights, should the glass scope break. The U.S. military M82 rifles are often equipped with Leupold Mark 4 telescopic sights. The M82A1M (USMC M82A3) rifles have long Picatinny accessory rails mounted and US Optics telescopic sights. Every M82 rifle is equipped with a folding carrying handle and a folding bipod (both are detachable on the M82A3). The M82A3 is also fitted with a detachable rear monopod under the butt. The buttpad is fitted with a soft recoil pad to further decrease the felt recoil. M82A1 and M82A3 rifles could be mounted on the M3 or M122 infantry tripods (originally intended for machine guns) or on vehicles using the special Barrett soft-mount. The M82A1 can be fitted with a carry sling but according to those who carried it in the field, the M82 is too uncomfortable to be carried on a sling due to its excessive length and weight. It is usually carried in a special carry soft or hard case.

The M82A2 differed from M82A1 mostly in its configuration— the pistol grip along with trigger was placed ahead of the magazine, and the buttpad placed below the receiver, just after the magazine. An additional forward grip was added below the receiver, and the scope mount moved forward.

The maximum effective range of the M107 is 1,830 metres (2,000 yd). The maximum range of this weapon (specifically the M107 variant) is 4,000 metres (4,400 yd), as quoted in the owner's manual. Fifty caliber (and larger) rounds have the potential to travel great distances if fired in an artillery-like fashion, necessitating the observance of large safety margins when firing on a range.

Variants:
M82 - 
12.7×99mm Barrett M82 semi-automatic rifle.
M82A1 - 
"Improved" M82; redesigned muzzle brake
M82A1A - 
Optimized for Mk 211 Mod 0 12.7mm ammunition
M82A1M - 
Rear grip; provision for monopod; redesigned rail
M82A2 - 
Shoulder-fired bullpup configuration
M82A3 - 
New production rifles built to M82A1M specifications, featuring lengthened accessory rail which is usually, but not always, raised higher up than the M82A1M/M107. Unlike the M82A1M/M107, it does not include rear grip and monopod socket
M90 - 
Bullpup Design; bolt-action alternative to semi-automatic M82 series
M95 - 
"Improved" Barrett M90; bullpup design; bolt-action operation
XM107/M107 - 
Initially used to designate 12.7×99mm Barrett M95 bolt-action rifle. Designation changed to apply to a product improved M82A1M variant. Includes lengthened accessory rail, rear grip, and monopod socket.
M107A1 - 
Improved variant of M107/M82. Features stronger construction with a 4 lb reduction in overall weight. Includes a retractable monopod, redesigned stock, thermal-guard cheek-piece, and a four-port muzzle brake designed for use with a sound/flash suppressor.
XM109 "Barrett Payload Rifle" - 
Experimental OSW based on M82A1; shortened 25mm barrel for firing high-explosive catridges
XM500 - 
Currently in development; gas-operated, semi-automatic operation; light/compact bullpup configuration; based on M82/M107; picatinny rail; adjustable bipod
G82 - 
German Army Designation for M107
Mrg M/95 - 
Denmark designation for Barrett M95
12.7 TKIV 2000 - 
Finnish Designation for M82A1
12.7 MOR - 
Norwegian Designation for M82A1
Ag 90 - 
Swedish Designation for M82A1
M99 - 
Netherlands Barrett M99

Specifications
M82A1
Caliber: 
.50 BMG (12.7×99mm) and .416 Barrett (10.6×83mm)
Operation: 
short recoil, semi-automatic
Overall length: 
57 inches (145 cm) w/ 29 inch (73.7 cm) barrel or 48 inches (122 cm) w/ 20 inch (50.8 cm) barrel
Barrel length: 
508 millimetres (20.0 in) or 737 mm (29.0 in)
Feed device: 
11-round detachable box magazine
Sights: 
Flip up, optics vary by user preference
Weight: 
30.9 lb (14.0 kg) w/ 29 inch (73.7 cm) barrel or 29.7 lb (13.5 kg) w/ 20 inch (50.8 cm) barrel
Muzzle velocity with 660 grain, 42.8 g projectile: 853 m/s (2,800 ft/s) with 400 grain, 26.0 g solid brass projectile: 990 m/s (3,200 ft/s)
Effective range: 
1,800 m (5,900 ft)
Maximum Range: 
6,812 m (22,349 ft)
Expected accuracy: 
Sub-MOA with match ammo
Unit replacement cost: 
$8,900 US

M82A2
Caliber: 
.50 BMG (12.7×99mm)
Length: 
1,409 mm (55.5 in)
Barrel length: 
737 mm (29.0 in)
Weight (unloaded): 
14.75 kg (32.5 lb)
Effective range on equipment-sized targets: 
2,000 m (6,600 ft)
Muzzle velocity: 
900 m/s (3,000 ft/s)
Magazine capacity: 
10 rounds
Unit replacement cost: 
$6,000
Status: 
Prototype seeing combat in Iraq

M107
Caliber: 
.50 BMG (12.7×99mm)
Length: 
1,448 mm (57.0 in)
Barrel length: 
737 mm (29.0 in)
Weight (unloaded w/ scope): 
12.9 kg (28.4 lb)
Magazine capacity: 
11 rounds
Weight of magazine: 
1.87 kg (4.1 lb)
Accuracy: 
3 Minutes of Angle (MOA)
Muzzle velocity: 
853 m/s (2,800 ft/s)
Effective Range: 
1,829 m (6,001 ft)
Maximum Range: 
6,812 m (22,349 ft)

XM500
Bullpup
Caliber: 
.50 BMG (12.7×99mm)
Length: 
1,168 millimetres (46.0 in)
Operation: 
gas operated, semi-automatic
Barrel: 
447 millimetres (17.6 in)
Weight: 
11.8 kg (26.0 lb)
Feed device: 
10-round detachable box magazine