The 270 cartridges family gains traction with Nosler’s M48 rifles chambered for the fastest 270 on the market, the 27 Nosler. Action length is the same as the old 270 Winchester.
Equally significant is the 27 Nosler’s recommended twist rate: 1 turn in 8.5 inches. Why so fast? To stabilize new, long, high B.C. bullets like the 165-grain AccuBond Long Range (B.C. .62,) the 170-grain Berger EOL Elite Hunter (G1 B.C. .662,) and Sierra’s 175-grain TGK. Hunters don’t always need such long, heavy bullets, but those high B.C. bullets minimize wind deflection and maximize retained energy at long range. (Or you can just stalk closer and to heck with pushing the envelop.)
With its case capacity (98.4 grains water compared to about 80 grains in a 270 Wby. Mag.,) the 27 Nosler should be able to nudge a 165-grain along at 3,150 fps, perhaps 3,200 fps, making this the fastest 270 cartridge in the world unless…
Unless Sig Sauer’s new 277 SIG Fury beats it.
277 SIG Fury Unique Among 270 Cartridges
The new Sig round is wildly different because it’s been chronographed spitting 140-grain .277 bullets 3,000 fps — from a 16-inch barrel. Figure another 30 fps velocity increase for every inch of barrel added and a 24-inch launchpad could nudged that 140-grain to 3,240 fps. Clearly that won’t touch the 27 Nosler, but that’s not surprising because the 277 SIG Fury case is the same length and diameter as the 308 Winchester. Yes, this is a short-action, small-capacity case which demands we ask the obvious question: how is it shooting as fast from a 16-inch barrel as the larger 270 Winchester shoots from a 24-inch barrel?
The answer is higher allowed chamber pressure. Super pressure. The 270 Winchester’s SAAMI spec maximum chamber pressure is 65,000 psi. The SIG Furry’s is 80,000 psi. To contain those pressures, the SIG cartridge is built with a stainless steel head. The main body, however, is brass. This gives it the necessary elasticity to expand and seal the chamber while the stronger steel head keeps the back end from rupturing.
Special Cartridge Construction Required For 277 Fury
The pieces of the 277 Furry case are assembled via an internal pressure ring of some kind near the base. I’m not exactly sure how it’s accomplished, but it involves plenty of pressure, I’m sure. The included photo of a model/mock up is close but not exact. In real life a lip of the brass wall gets rolled and pinched under the steel, I’ve been told.
New 270 Cartridges Challenge 6.5s and 7mms — Ron Spomer Outdoors is written by Ron Spomer for www.ronspomeroutdoors.com