6.5-284 Winchester (using Sierra bullets)
Date: Apr 21 2020
The 6.5-284 Cartridges origins date back to 1963, when Winchester introduced the .284 Winchester in the Model 88 lever action and Model 100 auto-loading rifle. The new 7mm cartridge was designed more or less to duplicate the ballistics of the widely popular .270 Winchester and the .280 Remington. However, the short-action cartridge was designed to be housed in any .308 Winchester-length action, and it produced low extreme velocity spreads and outstanding accuracy.
The .284 was and advanced cartridge and was not based on any existing case. It was beltless with a rebated rim that measured .473 inch (same as the .30-06 Springfield); however, the relatively fat case served to compared with other popular cartridges of that era, the shoulder angle was a comparatively steep 35 degrees. Maximum average pressure was established at 54,000 CUP, which translates into outstanding cartridge, but due to the lack of being chambered in popular bolt-action rifles from Winchester and Remington, its success was limited.
It didn’t take long for wildcatters and accuracy-minded shooters to recognize the virtues of the .284 case, which resulted in it being necked up and down to other calibers including 6.5mm, which became known as the 6.5-284 Winchester. While there have been specification differences, the two most popular variations of this, wildcat include a short-action version wherein overall cartridge length is held to 2.800 inches to allow it to function in .308-length actions. The second version features bullets seated out of an overall length of up to 3.228 inches to achieve greater powder capacity and positions bullets close to the leade. This lengthened version requires a .30-06 length action and is the one that has been most popular in various accuracy competitions. Both versions are based on the .284 Winchester case simply necked down to 6.5mm without any other changes to the case of the shoulder.
Due to its extreme accuracy potential, low extreme velocity spreads, along with bullets of high ballistic coefficient and low drag, plus respectable barrel life, the 6.5-284 began to dominate in various high- power and long-range target competitions around the world. In 1999 the Swedish firm Norma introduced it commercially as the 6.5-284 Norma, initially, high-quality cases and components were offered, but in 2011 factory ammunition became available.
The new Norma cartridge was based on the long-action wildcat version, with an overall cartridge length established at 3.228 inches, a specified 1:9 twist rate and six lands, according to CIP. Norma and Nosler currently offer factory loads. For comparison with accompanying load data, the test rifle used pushed the Norma 140-grain Partition factory load to 2,820 fps While the Nosler 120-grain Ballistic Tip load provided 3,022 fps, and the 140-grain AccuBond load reached 2,702 fps.
The accompanying data was fired using Sierra bullets seated to various overall cartridge lengths. When using loads that exceed 2.800 inches in length, be certain they are only fired in chambers featuring the longer throat, or cartridge may not chamber, or worse, pressure can become excessive.
Almost all powder chargers utilized with the 6.5-284 are below 55.0 grains, so do not require a magnum primer to achieve reliable ignition. Standard primers will generally offer lower extreme velocity spreads, and therefore better accuracy.