.220 Swift

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.220 Swift
.220 Swift (center) with .223 Rem (left) and .308 Win (right).
Type	Rifle
Place of origin	United States
Production history
Designer	Winchester
Designed	1935
Manufacturer	Winchester
Produced	1935–present
Variants	Wilson-Wotkyns .220 Arrow[1]
Specifications
Parent case	6mm Lee Navy
Case type	Semi-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 length	2.205 in (56.0 mm)
Overall length	2.680, 2.580 H.P. bullets
Case capacity	47 gr H2O (3.0 cm3)
Rifling twist	1 in 14–16 in (360–410 mm)
Primer type	Large rifle
Maximum pressure	62,000 psi (430 MPa)
Maximum CUP	54,000[2] 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[3]

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).^[4]