Search results
Results from the WOW.Com Content Network
The rifling twist rate for this cartridge is 177.8 mm (1 in 7 in), 6 grooves right hand twist, Ø lands = 5.56 millimetres (0.219 in), Ø grooves = 5.69 millimetres (0.224 in). [6] According to STANAG 4172 and the official NATO proofing guidelines the 5.56×45mm NATO case can handle up to 420.0 MPa (60,916 psi) piezo service pressure.
NATO chose a 178-mm (1-in-7) rifling twist rate for the 5.56×45mm NATO chambering. The SS109/M855 5.56×45mm NATO ball cartridge requires a 228 mm (1-in-9) twist rate, while adequately stabilizing the longer NATO L110/M856 5.56×45mm NATO tracer projectile requires an even faster 178 mm (1-in-7) twist rate.
The barrel has a chrome-lined bore with 6 right-hand grooves and a 178 mm (1:7 in) rifling twist rate that is optimized for use with heavier SS109 5.56×45mm NATO rounds. A barrel with a 305 mm (1:12 in) twist rate designed specifically to stabilize the lightweight M193 cartridge is also available. [2]
The barrel rifling was revised to a faster 1:7 (178 mm) twist rate to adequately stabilize the new 5.56×45mm NATO SS109/M855 ball and L110/M856 tracer ammunition.
The rifled barrel has 6 right-hand grooves and the Swiss Army specification 254 mm (1:10 in) rifling twist rate is optimized for Swiss military GP 90 ammunition. An export-oriented 5.56×45mm NATO barrel configuration with a 178 mm (1:7 in) twist rate is also available, to adequately stabilize the relatively long NATO L110/M856 5.56×45mm NATO ...
The rifle's barrel features 6 right-hand grooves and a rifling twist rate of 1 in 178 mm (1:7 in); it is fitted with an open-type 3-prong flash suppressor, and later a "birdcage" style one, both designed to launch rifle grenades. The weapon will also mount a knife-type bayonet.
Early models had barrels with a 1:12 rate of twist for the original .223 Remington, 55-grain (3.6 g) bullets. Current models have barrels with a 1:9 or 1:7 twist rate for the 5.56×45mm NATO, 62-grain (4.0 g) bullets.
The Model 0000 rifle and Model 6000 carbine use a slower 305 mm (1:12 in) twist rate for the shorter and lighter American M193 bullet. Fabrique Nationale also offers semi-automatic-only Law Enforcement carbine versions: [citation needed] the Model 7030 with a 178 mm (1:7 in) rifling twist and the Model 6040 with a 305 mm (1:12 in) twist rate ...