.270 Winchester

.270 Winchester
From left: .25-06, .270 Winchester, .280 Remington, .30-06, .35 Whelen
Type	Rifle / hunting
Place of origin	United States
Production history
Designer	Winchester
Designed	1923
Manufacturer	Winchester
Produced	1925–present
Specifications
Parent case	.30-06 Springfield
Case type	Rimless, bottleneck
Bullet diameter	.277 in (7.0 mm)
Land diameter	.270 in (6.9 mm)
Neck diameter	.308 in (7.8 mm)
Shoulder diameter	.441 in (11.2 mm)
Base diameter	.470 in (11.9 mm)
Rim diameter	.473 in (12.0 mm)
Case length	2.540 in (64.5 mm)
Overall length	3.340 in (84.8 mm)
Case capacity	67 gr H2O (4.3 cm3)
Rifling twist	1 in 10 in (250 mm)
Primer type	Large rifle
Maximum pressure (C.I.P.)	62,366 psi (430.00 MPa)
Maximum pressure (SAAMI)	65,000 psi (450 MPa)
Ballistic performance
Bullet mass/type Velocity Energy 90 gr (6 g) HP 3,603 ft/s (1,098 m/s) 2,595 ft⋅lbf (3,518 J) 130 gr (8 g) SP 3,060 ft/s (930 m/s) 2,702 ft⋅lbf (3,663 J) 140 gr (9 g) SP 2,950 ft/s (900 m/s) 2,705 ft⋅lbf (3,667 J) 150 gr (10 g) SP 2,850 ft/s (870 m/s) 2,705 ft⋅lbf (3,667 J) 130 gr (8 g) SST 3,050 ft/s (930 m/s) 2,685 ft⋅lbf (3,640 J)
Source(s): Norma, Hodgdon,[1] Hornady[2]

The .270 Winchester is a rifle cartridge developed by Winchester Repeating Arms Company in 1923, and it was unveiled in 1925 as a chambering for their bolt-action Model 54^[3] to become arguably the flattest shooting cartridge of its day, only competing with the .300 Holland & Holland Magnum, also introduced in the same year.^[4]

The .270 Winchester was derived from the .30-06 Springfield and the bore diameter was likely^[5] inspired by 7mm Mauser. The .270 Winchester uses a .270 inch (6.86 mm) bore diameter and a .277 inch (7.04 mm) bullet diameter.