| .284 Winchester | ||||||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
 .284 Winchester (center) with .308 Win (left) and 7mm Remington Magnum (right) | ||||||||||||||||||||
| Type | Rifle | |||||||||||||||||||
| Place of origin | United States | |||||||||||||||||||
| Production history | ||||||||||||||||||||
| Designer | Winchester | |||||||||||||||||||
| Designed | 1963 | |||||||||||||||||||
| Manufacturer | Winchester | |||||||||||||||||||
| Produced | 1963–present | |||||||||||||||||||
| Specifications | ||||||||||||||||||||
| Case type | rebated rim, bottleneck | |||||||||||||||||||
| Bullet diameter | 7.21 mm (0.284 in) | |||||||||||||||||||
| Land diameter | 7.00 mm (0.276 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 | 1.37 mm (0.054 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) | |||||||||||||||||||
| Maximum pressure (SAAMI) | 386 MPa (56,000 psi) | |||||||||||||||||||
| Ballistic performance | ||||||||||||||||||||
| ||||||||||||||||||||
| Test barrel length: 24 in (610 mm) Source(s): Winchester Ammunition Accurate Powder [1] | ||||||||||||||||||||
The .284 Winchester (7.21x55mmRB) is a rebated rim firearm cartridge, introduced by Winchester in 1963.
The .284 Winchester was designed to achieve .270 Winchester and .280 Remington performance from the new Winchester Model 100 autoloader and Winchester Model 88 lever-action rifles. The 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.[citation needed]
.284 Winchester has enjoyed a resurgence due to interest from long-range competitive shooters. Winchester has continued to produce brass cases for this cartridge since 1963.[2]