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It also has the fastest rifling twist ratio for the .223 Remington of the three models(1:9 instead of 1:12). Early production rifles had a 1:12 twist rate and post-2014 rifles have the 1:9 twist rate. [2] The CZ 527 Varmint in .223 has muzzle velocities for standard-load 45-grain (2.9 g) ammunition of around 3,500 feet per second (1,100 m/s).
If a 5.56×45mm NATO cartridge is loaded into a chamber intended to use .223 Remington, the bullet will be in contact with the rifling and the forcing cone is very tight. This generates a much higher pressure than .223 Remington chambers are designed for. [3] NATO chose a 178-mm (1-in-7) rifling twist rate for the 5.56×45mm NATO chambering.
1:14: 1 right hand twist every 14 inches (356 mm) .222 Remington or .223 Remington (US M193) 1:12: 1 right hand twist every 12 inches (305 mm) .223 Remington (US M193) or 7.62×39mm; 1:10: 1 right hand twist every 10 inches (254 mm) 9×19mm NATO; 1:9: 1 right hand twist every 9 inches (229 mm) .223 Remington & 5.56×45mm NATO
The AR-15 rifle usually comes chambered for either the military cartridge 5.56×45mm or the .223 Remington. Because of the pressures associated with the 5.56×45mm, it is not advisable to fire 5.56×45mm rounds in an AR-15 marked as .223 Remington, since this can result in damage to the rifle or injury to the shooter. [1]
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.
Weapons designed to adequately stabilize both the M193 or SS109 projectiles (like civilian market clones) usually have a six-groove, right-hand twist, one turn in 9 inches (1:228.6 mm or 41.1 calibers) or one turn in 8 inches (1:203.2 mm or 36.5 calibers) bore, although other and 1:7 inches twist rates are available as well.
Soon after the release of the .223 Remington as a commercial cartridge, shooters began experimenting with the cartridge in an attempt to improve its performance. [1] Several of these experimenters necked up the .223 Remington to 6mm as the .243 inches (6.17 mm) caliber bullets provided better external ballistic performance over .224 inches (5. ...
0.405 [5] 56.72mm Same cartridge as .244 Remington and interchangeable. Rifles marked .244 Remington may not stabilize heaviest 6mm Remington bullets. [3] 6mm BR Norma: 1996 [14] Sweden 3 [15] [16] R 6x39.6mm 2789 [15] 0.243 0.517 [15] 39.6mm Norma's redesigned of the Remington 6mm BR in order to utilize VLD bullets. 6mm XC: 2000 US 4 [17] [18 ...