The .277 Wolverine is a wildcat cartridge. It is a multi-purpose mid-power cartridge with increased ballistic performance over the AR-15's traditional.223 Remington cartridge requiring only a new barrel to upgrade/convert any 5.56-based firearm to.277 Wolverine.
Design
For fundamentally the same reasons that a.277 inch diameter bullet was selected for the 6.8mm Remington SPC, selected 6.8mm as the basis for a new AR-15 wildcat. Like the.300 AAC Blackout and unlike the 6.8 SPC and other "larger bore" AR-15 cartridges, the.277 Wolverine is based on the widely available 5.56×45mm parent case. Therefore, rifle components such as the bolt and magazine are interchangeable between 5.56×45mm and.277 Wolverine firearms, and standard AR-15 magazines can be used with no loss of capacity. A new barrel is the minimum required component to convert a standard AR-15 to.277 Wolverine. In order to load heavier bullets to magazine length without the problems of seating the bullet's ogive into the case mouth, the Wolverine case is shortened to approximately 39 mm from its 45 mm parent brass. The case is resized and formed in a single-step operation to create new 23-degree shoulder and larger neck. Initial design focused on optimal performance with supersonic bullets in the 85-115 gr class, therefore a 1:11 twist rate barrel with 5R rifling was selected. Subsequent consumer interest in firing "heavy-for-caliber" subsonic bullets led to the design, testing, and production of 1:7 twist barrels to stabilize the longer heavier bullets.
Development
Initially developed, tested, and marketed as a proprietary cartridge, MDWS publicly released the detailed chamber and headspace gage specifications/drawings for the.277 Wolverine in June 2015. At least four commercial manufacturers have produced.277 Wolverine barrels, mostly for AR-15 conversions – although MDWS also sells barrels for Savage and Remington bolt-action rifles. Barrel manufacturers include: X-Caliber, McGowen, AR Precision, and PAC-NOR. By the end of April 2016, more than 1,000.277 Wolverine barrels had been sold, with more than 2,000 by mid-November 2017. Barrels lengths include: 8.2, 10.5, 12.5, and 14.5 inch pistol; 16, 18, and 20 inch rifle. .277 Wolverine cases are easily made by the hobbyist reloader from plentiful and inexpensive 5.56×45mm brass. Extensive reloading data is available. Ready-to-load brass and/or loaded ammunition is available commercially from several sources including: JB's Firearms, LLC and OutdoorShooterSupply. Reloading dies and tools are available from Hornady, Lee Precision, Sheridan Engineering, CH4D, and Little Crow Gun Works. The fire-formed.277 Wolverine case holds approximately 27.5-27.8 gr of water, compared to 28.5-28.8 gr for the parent case. In October 2017, Starline produced 50,000 newly manufactured cases head-stamped ".277 WLV" for MDWS; all were sold in under 72 hours of posting. Starline lists the.277 Wolverine on their website as a standard offering.
Performance
The.277 Wolverine has shown comparable performance to the 6.8 SPC with 110 gr bullets, achieving similar muzzle velocities of 2,500 fps vs. 2,700 fps. The smaller case of the.277 Wolverine is more efficient and has less recoil due to its smaller propellant load. With lighter bullets, 80-90 gr, although slower than typical 5.56×45mm rounds, the.277 Wolverine provides substantially increased energy due to greater mass. For example, 60-62 gr bullets from a 5.56×45mm round typically provide less than 1,200 ft·lbs of energy, while 85-90 gr bullets from a.277 Wolverine round provide over 1,500 ft·lbs of energy. There are always trade-offs between cartridge size, bullet diameter and weight, muzzle velocity, and energy on-target. The.277 Wolverine will never replace larger high-power cartridges such as the.308 Winchester or.270 Winchester for long range shooting; however – it outperforms the.223 Remington at typical hunting ranges and approaches the 6.8 SPC while using less expensive components. The following table provides comparative performance data for several factory cartridges in the mid-power AR-15 class:
The.277 Wolverine provides similar ballistic performance to the 6.8 SPC for accuracy, hunting, target shooting, and home/personal defense. 277/6.8mm bullets are widely available from virtually all major and many boutique reloading component manufactures in a wide range of bullet weights from 85 to 200 grains and styles useful in the.277 Wolverine - including lead-free practice, competition target, varmint, defensive, and game hunting. The complete bolt carrier group and charging handle can be swapped between the original 5.56×45 and the.277 Wolverine upper.
Comparisons
A very wide range of cartridges from diminutive.17 rimfire to massive.50 caliber rounds have been used in AR-15 rifles. The.277 WLV provides medium bore performance exceeding the parent 5.56×45 cartridge and the.300 BLK while approaching the power of the larger 6.8 SPC which requires larger cases and dedicated components. Per an interview with the cartridge's designer: "I liked the performance of the 6.8 SPC and the versatility of the 300 Blackout. After researching both of them extensively, and having a lot of conversations with many, many experienced professionals and enthusiasts, I decided to move forward with a new cartridge design that would hopefully combine the attributes of both, and dismiss the deficiencies."
