.220 Swift

The .220 Swift (5.56×56mmSR) is a semi-rimmed rifle cartridge developed by Winchester and introduced in 1935 for small game and varmint hunting. It was the first factory-loaded rifle cartridge with a muzzle velocity of over 1,200 m/s (4,000 ft/s).

This article is about the rifle cartridge. For the short story ".220 Swift", see Karl Edward Wagner.

.220 Swift
.220 Swift (center) with .223 Rem (left) and .308 Win (right).
TypeRifle
Place of originUnited States
Production history
DesignerWinchester
Designed1935
ManufacturerWinchester
Produced1935–present
VariantsWilson-Wotkyns .220 Arrow
Specifications
Parent case6mm Lee Navy
Case typeSemi-rimmed, bottleneck
Bullet diameter.224 in (5.7 mm)
Neck diameter.260 in (6.6 mm)
Shoulder diameter.402 in (10.2 mm)
Base diameter.445 in (11.3 mm)
Rim diameter.473 in (12.0 mm)
Case length2.205 in (56.0 mm)
Overall length2.680, 2.580 H.P. bullets
Case capacity47 gr H2O (3.0 cm3)
Rifling twist1 in 14–16 in (360–410 mm)
Primer typeLarge rifle
Maximum pressure62,000 psi (430 MPa)
Maximum CUP54,000 CUP
Ballistic performance
Bullet mass/type Velocity Energy
40 gr (3 g) HP 4,213 ft/s (1,284 m/s) 1,577 ft⋅lbf (2,138 J)
50 gr (3 g) SP 3,947 ft/s (1,203 m/s) 1,800 ft⋅lbf (2,400 J)
55 gr (4 g) SP 3,839 ft/s (1,170 m/s) 1,800 ft⋅lbf (2,400 J)
60 gr (4 g) SP 3,647 ft/s (1,112 m/s) 1,772 ft⋅lbf (2,403 J)
Source(s): Hodgdon
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