5.56×45mm NATO

The 5.56×45mm NATO (official NATO nomenclature 5.56 NATO, commonly pronounced "five-five-six") is a rimless bottlenecked intermediate cartridge family developed in the late 1970s in Belgium by FN Herstal. It consists of the SS109, L110, and SS111 cartridges. On 28 October 1980, under STANAG 4172, it was standardized as the second standard service rifle cartridge for NATO forces as well as many non-NATO countries. Though they are not entirely identical, the 5.56×45mm NATO cartridge family was derived from and is dimensionally similar to the .223 Remington cartridge designed by Remington Arms in the early 1960s.

"NATO round" redirects here. For the larger cartridge, see 7.62×51mm NATO. For the even larger 12.7×99mm NATO cartridge, see .50 BMG.

5.56×45mm NATO
5.56×45mm NATO with measurement, left to right: Bullet, case, and complete cartridge
TypeRifle, carbine, DMR, and LMG
Place of originBelgium
Service history
In service1980–present
Used byNATO, Japan, South Korea, Taiwan, Australia, other major non-NATO allies
Production history
DesignerFN Herstal
Designedlate 1970s–1980
Specifications
Parent case.223 Remington (M193)
Case typeRimless tapered, bottleneck
Bullet diameter5.70 mm (0.224 in)
Land diameter5.56 mm (0.219 in)
Neck diameter6.43 mm (0.253 in)
Shoulder diameter9.00 mm (0.354 in)
Base diameter9.58 mm (0.377 in)
Rim diameter9.60 mm (0.378 in)
Rim thickness1.14 mm (0.045 in)
Case length44.70 mm (1.760 in)
Overall length57.40 mm (2.260 in)
Case capacity1.85 cm3 (28.5 gr H2O)
Rifling twist1 in 7 in (178 mm) or 1 in 9 in (229 mm)
Primer typeSmall rifle
Maximum pressure (EPVAT)430.00 MPa (62,366 psi)
Maximum pressure (SCATP 5.56)380.00 MPa (55,114 psi)
Ballistic performance
Bullet mass/type Velocity Energy
3.56 g (55 gr) XM193 FMJBT 993 m/s (3,260 ft/s) 1,755 J (1,294 ft⋅lbf)
4 g (62 gr) SS109 FMJBT 948 m/s (3,110 ft/s) 1,797 J (1,325 ft⋅lbf)
4 g (62 gr) M855A1 FMJBT 961 m/s (3,150 ft/s) 1,859 J (1,371 ft⋅lbf)
4.1 g (63 gr) DM11 FMJBT 856 m/s (2,810 ft/s) 1,796 J (1,325 ft⋅lbf)
4.1 g (63 gr) GP 90 FMJBT 851 m/s (2,790 ft/s) 1,679 J (1,238 ft⋅lbf)
Test barrel length: 508 mm (20.0 in)
Source(s): NATO EPVAT testing, QuickLOAD, SAAMI, C.I.P.
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