A wildcat cartridge is an ammunition choice that is not widely mass produced, and generally originates from reloading trial and errors to help diversify a specific shooting experience. It’s a popular pastime for reloading enthusiasts, and often results in some pretty powerful options that may be picked up by major ammo manufacturers.
The 277 Wolverine is one such round, and was introduced by Mad Dog Weapon Systems as an upgrade to the ever favorite 5.56 x 45mm. Although it hasn’t gained as much popularity as other simple AR-15 platform modifications, it is well worth comparing the 277 Wolverine vs 300 Blackout- and have a little fun shooting both on the range.
What’s The Difference Between The 277 Wolverine VS 300 BLK Rounds?
Since both rounds are built off the 5.56 x 45mm cartridge, there isn’t a whole lot of difference between these two- unless you include their availability. Side by side they are fairly comparable in both size ballistics, but since the Wolverine was made to perform similarly to a 6.8SPC, while embracing the versatility of the 300 BLK- there are some perks worth noting.
Comparison Between 277 Wolverine And 300 BLK Rounds
The 300 BLK was born of the need for a lethal close range option following military specs, while the Wolverine was specifically created to improve the performance of the AR platform without having to change too much hardware.
Specifications
277 Wolverine
300 Blackout


Brand
Mad Dog Weapons Systems (110 gr)
AAC (125 gr)
Bullet Size
Bullet Size: 2.26 inches
Bullet Diameter: 0.277 inches
Shell Case Length: 1.530 – 1.545 inches
Bullet Size: 2.26 inches
Bullet Diameter: 0.308 inches
Shell Case Length: 1.368 inches
Energy (per 200 yards)
776 ft-lbs
824 ft⋅lbs
Velocity (per 200 yards)
1782 ft/s
1,872 ft/s
Muzzle Energy/Velocity
1525 / 2500
1360 / 2215
277 Wolverine

Brand
Mad Dog Weapons Systems (110 gr)
Bullet Size
Bullet Size: 2.26 inches
Bullet Diameter: 0.277 inches
Shell Case Length: 1.530 – 1.545 inches
Energy (per 200 yards)
776 ft-lbs
Velocity (per 200 yards)
1782 ft/s
Muzzle Energy/Velocity
1525 / 2500
300 Blackout

Brand
AAC (125 gr)
Bullet Size
Bullet Size: 2.26 inches
Bullet Diameter: 0.308 inches
Shell Case Length: 1.368 inches
Energy (per 200 yards)
824 ft⋅lbs
Velocity (per 200 yards)
1,872 ft/s
Muzzle Energy/Velocity
1360 / 2215
277 Wolverine
Introduced in 2015, the 277 Wolverine is a wildcat cartridge created by Mark Kexel of Mad Dog Weapon Systems. This novice reloader began dreaming up the round as a kid, and desired to create an option that found a balance between a 6.8 and .300 in an easy to convert 5.56 AR platform.
Features
Easily converted from a 5.56 casing, the 277 Wolverine simply requires a resizing of the neck to form a new shoulder, and a trim of the neck to the proper length. Easy for reloaders to make on their own, there also are a few manufacturers offering loaded rounds, as well as presized casing.
This is a slightly longer case than the 300 Blackout, and offers a flatter trajectory and more overall energy. It is easy to shoot from a standard 5.56 platform with a modified barrel, which has become more and more available for easy conversion due to the attention the bullet is getting.
Great for self defense, it has all the perks of the 300 BLK close range power, and offers incredible accuracy and lethality for big game up to 300 yards- which makes easy targets of smaller game at even further distances.
Pros
This option provides a significant boost to the 5.56/.223 go-to, and has the capabilities of enhancing the modern sporting rifle experience. The fact that it is incredibly easy to use with existing AR-15 platform firearms, and works with all the hardware, including mags with a simple barrel change- creates an affordable upgrade as well.
As explained, it was born of a desire to take everything awesome from the 6.8 and .300 and make something that minimized any issues either had. And it has succeeded, offering the ballistic performance of the 6.8SPC alongside the subsonic and supersonic versitalities of the 300 BLK. It should be noted it can easily work in both short and long barrels as well, thus taking one more page from the 300 BLK round.
Cons
The biggest issue with the cartridge is its availability. Fairly new, it isn’t as widely offered and is only manufactured as a loaded cartridge by a handful of ammo supplies. As mentioned, premeasured and cut casings are available – and it can be loaded quite easily with a great range of powder and weight options. This makes it a fun option for your own reloading skills.
Bottom line- there is still a lot of room for growth, and it seems like it has a good foothold in the market to do so.
300 Blackout
The 300 Blackout has been around only slightly longer than the 277 Wolverine, and first made its appearance in 2011 as a solution for close range military combat. Incredibly versatile, it works well with both short and long barrels, and offers a great range of uses that includes everything from home defense to hunting and competitive shooting. These are also modified from the 5.56 round, and work in any standard AR-15 platform with a simple barrel change.
Features
The 300 BLK is a popular round that is easily found via quite a few ammo manufacturers. It is considered affordable and offers excellent accuracy with a lower recoil than many competitive options. Considered perfect for 100 to 200 yard lethal shots, it also can provide some great practice for 500+ yard shots and is considered the prime choice for anyone wanting to shoot subsonic, supersonic, or suppressed rounds; its versatility simply cannot be beaten.
Pros
Another perk it provided the 277 Wolverine is how well it handles a wide range of weights without sacrificing power. This aids in its overall versatility- and is an easy to reload option as well; handling light 78 gr bullets all the way up to a 245 gr bullet without issue. You can mix and match your loads also, making for a fun day on the range.
Plus, the easy 5.56/.233 AR modification only requires a new barrel, and you can leave the rest of the hardware alone. And yes, this includes the mags. If you have been looking for a way to change up an existing firearm, this is a budget friendly way to do so.
Cons
Like the 277, there isn’t a lot to get after concerning this round. The fact it works best between 100 and 200 yards may have long distance competitive shooters looking elsewhere, but it certainly can stand its ground for what it was made for. A suppressed subsonic load is considered the best way to take advantage of its full potential, but that doesn’t mean it isn’t any less accurate, or deadly, when used in any other manner.
277 Wolverine Stand Out Features
The 277 Wolverine stands out from the 300 Blackout simply because it was designed to take the best from the round to improve upon your shooting experience. The ability to shoot both supersonic, and subsonic loads, use it through both short and long barrels, and take advantage of a flatter trajectory without a loss of energy is the 300 BLK upgrade you have been looking for.
Conclusion
The ability of a simple barrel change completely overhauling your shooting experience with a new cartridge is an awesome thing. Wildcatting your own reloads can be a ton of fun, but if you aren’t a reloading fan- you can easily find some alternative rounds growing in popularity and manufacturing offers.
The 277 Wolverine is one such option, and takes everything that is awesome from the 300 BLK to create a seriously versatile, powerful, and dependable option for hunting and target acquisition.

277 Wolverine Overview
- Dependable energy and trajectory
- Perfect for 200 – 300 yard shots
- Great versatility options
- Easy AR .223/5.56 platform modification

300 BLK
Overview
- Dependable and efficient
- Easy AR .223/5.56 platform modification
- Low recoil and comfortable to shoot
- Huge array of shooting scenarios, including subsonic, supersonic, and suppressed
If you’ve had a chance to shoot either round, we’d love to hear about your experiences below- and what detail you feel should be mentioned that we may have missed. And, as always, please share!