.277 Wolverine
The .277 Wolverine (6.8×39mm) is a wildcat cartridge based on the 5.56x45mm NATO round and was designed by Mark Kexel of Mad Dog Weapon Systems in 2014. It is a versatile mid-powered cartridge with better ballistic performance over the AR-15's traditional .223 Remington / 5.56×45mm NATO chamberings. Converting from .223 / 5.56 to the .277 Wolverine requires only a new barrel. It utilizes small rifle primers, as well as .277 caliber projectiles (like the similar 6.8 SPC, the .270 Winchester, as well as the highly anticipated .27 Nosler and .277 Fury).
One major difference between the .277 Wolverine and cartridges such as the 6.5 Grendel or 6.8 SPC, is that the Wolverine is directly based on the 5.56 cartridge and is merely necked up to accept a larger caliber bullet. This is the same design philosophy used on rounds like the .300 Whisper and .300 Blackout. As a result, the round can feed from a standard AR-15 / STANAG magazine. It also means that magazine capacity is not hindered in any way.
