BUY BUY PMC 5.56 AMMO 62gr 20rd ONLINE
ORDER PMC 5.56 AMMO 62gr 20rd ONLINE NOW, INSTANT DELIVERY
Rifle barrel configurations
When 5.56×45mm NATO was adopted as standard in 1980, NATO chose a 178 mm (1:7) rifling twist rate for the 5.56×45mm NATO chambering to adequately stabilize the relatively long NATO L110/M856 5.56×45mm NATO tracer projectile. The US at that time converted all rifles in inventory by replacing the barrels and all new US military rifles since have been manufactured with this ratio.
In the US builders of AR type rifles can specify barrels with either .223 Remington, .223 Wylde, 223 Noveske, or 5.56×45mm NATO chambers in lengths from pistol (7.5″) to long rifle (24″). These barrels are also available with rifling ranging from 356 mm (1-in-14″) to 178 mm (1-in-7″). US makers are moving toward 5.56×45mm NATO and 178 mm (1-in-7″), which will ensure the least liability. Bolt action rifles have few options in this regard. Those chambered for .223 Remington may not have a fast enough rifling to stabilize the longer 5.56×45mm NATO bullets which range up to 77 gr. Some hunting loads of .223 Remington go to 90 grains.
The 5.56×45mm NATO SS109/M855 cartridge (NATO: SS109; U.S.: M855) with standard 62 gr. lead core bullets with steel penetrator will penetrate about 38 to 51 cm (15 to 20 in) into soft tissue in ideal circumstances. As with all spitzer shaped projectiles, it is prone to yaw in soft tissue. However, at impact velocities above roughly 762 m/s (2,500 ft/s), it may yaw and then fragment at the cannelure (the crimping groove around the cylinder of the bullet). These fragments can disperse through flesh and bone, inflicting additional internal injuries.
Fragmentation, if and when it occurs, imparts much greater damage to human tissue than bullet dimensions and velocities would suggest. This fragmentation effect is highly dependent on velocity, and therefore barrel length: short-barreled carbines generate less muzzle velocity and therefore lose wounding effectiveness at much shorter ranges than longer-barreled rifles.
Proponents of the hydrostatic shock theory contend that the shockwave from a high-velocity bullet results in wounding effects beyond the tissue directly crushed and torn by the bullet and fragments. However, others argue that tissue damage from hydrostatic shock is a myth. Critics argue that sonic pressure waves do not cause tissue disruption and that temporary cavity formation is the actual cause of tissue disruption mistakenly attributed to sonic pressure waves.
SS109/M855 NATO ball can penetrate up to 3 mm (0.12 in) of steel at 600 meters. According to Nammo, a Finnish-Norwegian ammunition producer, the 5.56×45mm NATO M995 armour piercing cartridge can penetrate up to 12 mm (0.47 in) of RHA steel at 100 meters.
The Swedish military has measured the bullet velocities of SS109/M855 military cartridges at 4 m (13.1 ft) from the muzzle fired from differing barrel lengths.
|Barrel length||SS109/M855 V4 bullet velocity||V4 velocity loss|
|210 mm (8.3 in)||723 m/s (2,372 ft/s)||41 m/s (135 ft/s)|
|240 mm (9.4 in)||764 m/s (2,507 ft/s)||32 m/s (105 ft/s)|
|270 mm (10.6 in)||796 m/s (2,612 ft/s)||29 m/s (95 ft/s)|
|300 mm (11.8 in)||825 m/s (2,707 ft/s)||18 m/s (59 ft/s)|
|330 mm (13.0 in)||843 m/s (2,766 ft/s)||23 m/s (75 ft/s)|
|360 mm (14.2 in)||866 m/s (2,841 ft/s)||12 m/s (39 ft/s)|
|390 mm (15.4 in)||878 m/s (2,881 ft/s)||14 m/s (46 ft/s)|
|420 mm (16.5 in)||892 m/s (2,927 ft/s)||14 m/s (46 ft/s)|
|450 mm (17.7 in)||906 m/s (2,972 ft/s)||9 m/s (30 ft/s)|
|480 mm (18.9 in)||915 m/s (3,002 ft/s)||7 m/s (23 ft/s)|
|508 mm (20.0 in)||922 m/s (3,025 ft/s)||–|