.284 Winchester

.284 Winchester (center) with .308 Win (left) and 7mm Remington Magnum (right).

Type

Rifle

Place of origin

United States

Service history

In service

never issued

Production history

Designer

Winchester

Designed

1963

Manufacturer

Winchester

Produced

1963–present

Specifications

Bullet diameter

7.21 mm (0.284 in)

Neck diameter

8.13 mm (0.320 in)

Shoulder diameter

12.06 mm (0.475 in)

Base diameter

12.72 mm (0.501 in)

Rim diameter

12.01 mm (0.473 in)

Rim thickness

1.02 mm (0.040 in)

Case length

55.12 mm (2.170 in)

Overall length

71.12 mm (2.800 in)

Case capacity

4.29 cm³ (66.2 gr H₂O)

Rifling twist

254 mm (1 in 10 in)

Primer type

Large rifle

Maximum pressure (C.I.P.)

440.00 MPa (63,817 psi)

Ballistic performance

Bullet mass/type	Velocity	Energy
150 gr (10 g) Super-X Power-Point	2,860 ft/s (870 m/s)	2,724 ft·lbf (3,693 J)
100 gr (6 g) HDY 100 HP	3,175 ft/s (968 m/s)	2,238 ft·lbf (3,034 J)
120 gr (8 g) SPR 120 SP	2,968 ft/s (905 m/s)	2,347 ft·lbf (3,182 J)
139 gr (9 g) HDY 139 SP	2,845 ft/s (867 m/s)	2,498 ft·lbf (3,387 J)

Test barrel length: 24 in (610 mm)
Source(s): Winchester Ammunition Accurate Powder

The .284 Winchester is an example of a commercially unsuccessful cartridge that has enjoyed a resurgence due to interest from long-range competitive shooters. Introduced by Winchester in 1963, the .284 Winchester was designed to squeeze .270 Winchester and .280 Remington performance from the new Winchester Model 100 autoloader and Winchester Model 88 lever action rifles.

The end result was a 7 mm cartridge with about the same overall length as the .308 Winchester but with a wider body that yields a powder capacity about the same as that of the .270 Winchester and .280 Remington.

At one time the Savage Model 99 was available in .284 Winchester, and Ruger produced a small run of Ruger M77 rifles in this caliber, whereas Ultra Light Arms now builds more Model 20 rifles in .284 Winchester than all other calibers combined.

The .284 Winchester has 4.29 ml (66 grains H₂O) cartridge case capacity. The case has a rebated rim and a body almost as large in diameter as that of typical belted magnum cases.

.284 Winchester maximum C.I.P. cartridge dimensions. All sizes in millimeters (mm).

Americans would define the shoulder angle at alpha/2 = 35 degrees. The common rifling twist rate for this cartridge is 254 mm (1 in 10 in), 6 grooves, Ø lands = 7.00 mm, Ø grooves = 7.19 mm, land width = 2.79 mm and the primer type is large rifle.

According to the official C.I.P. guidelines the .284 Winchester case can handle up to 440 MPa (63,816 psi) piezo pressure. In C.I.P. regulated countries every rifle cartridge combo has to be proofed at 125% of this maximum C.I.P. pressure to certify for sale to consumers.
The SAAMI pressure limit for the .284 Winchester is set at 56,000 PSI, piezo pressure.

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Wikipedia