6.5mm-284 Norma (6.5mm-284 Win.)
By Chuck Hawks
Also known as the 6.5-284 Winchester, Norma standardized the 6.5mm-284 wildcat cartridge and as I write these words it has is the dominant cartridge in ultra-long range F-Class Open competition. As standardized, the CIP maximum average pressure (MAP) for the 6.5-284 Norma is actually 1000 psi higher than the SAAMI MAP for the 6.5mm Remington Magnum.The 6.5mm-284 combines the relatively short, fat case configuration popular with those who shoot single shot target rifles with the outstanding ballistic coefficient of 6.5mm match bullets. Savage Arms is producing an F-Class target rifle and many custom rifle builders chamber for the cartridge. Lapua, Norma and Nosler offer 6.5-284 match brass and the latter two companies offer factory loaded hunting ammunition in the caliber.
Nosler factory loads are available with their 120 grain Ballistic Tip bullet and Norma offers factory loads with that bullet and the 140 grain Nosler Partition bullet. The Norma loads have a catalog MV of 3117 fps with the 120 grain bullet and 2953 fps with the 140 grain bullet. The ME figures are 2589 ft. lbs. and 2712 ft. lbs. respectively.
The 6.5-284 is based on the .284 Winchester case necked-down to accept .264" (6.5mm) diameter bullets, which accounts for it sometimes being called the "6.5-284 Winchester." The .284 Win. case is a unique, rebated rim number used for no other factory produced cartridge.
These are the dimensions for the 6.5mm-284 shown in the sixth edition of the Hornady Handbook of Cartridge Reloading: Bullet diameter .264"; Maximum case length 2.170" (trim to 2.160"); Maximum cartridge overall length 2.80"; Rim diameter.473"; Base diameter .500"; Shoulder diameter .475"; Shoulder angle 35 degrees; Neck diameter .295".
The Hornady Handbook is a good source for 6.5mm-284 reloading data. They recommend VIHT N-165, IMR 4831, Win. WMR, and AA 3100 powders with the heavier 129 and 140 grain bullets for which a cartridge of this capacity would seem best suited.
Win. WMR powder gave top performance with both the 129 and 140 grain Hornady bullets in the 6.5-284. With the 129 grain bullets, 44.8 grains of WMR powder gave a MV of 2500 fps. A maximum load of 52.9 grains of WMR drove the same bullets to a MV of 2900 fps.
Using Hornady's 140 grain bullets in front of 43.6 grains of WMR yielded a MV of 2400 fps. And a maximum load of 49.7 grains of WMR gave the 140 grain bullets at a MV of 2700 fps. Winchester cases and Federal 210 primers were used for all of these Hornady loads, which were chronographed in a 24" rifle barrel.
F-Class shooters push the 6.5-284 to the limit, achieving abound 2950 fps with the 142 grain Sierra match bullet from their very long barreled rifles. It is interesting that the top velocities for the 6.5mm-284 are nearly identical to the top velocities for the 6.5mm Remington Magnum with the same bullet weights, only the 6.5mm Mag. can do it from shorter barrels. This makes me wonder why the 6.5mm Rem. Mag. is not making inroads in F-Class shooting.
Copyright 2007 by Chuck Hawks. All rights reserved.