Cumulatively, the various branches of the United States military form the greatest fighting force the world has ever seen. As a result, everyone from law enforcement professionals to casual recreational shooters pays close attention to the gear adopted by the armed forces. That statement holds true for the MK248 Mod 1 cartridge.

With the exception of AR-15 style weapon systems, the Mk 248 Mod 1 cartridge is perhaps the most popular piece of military equipment among shooting enthusiasts. This ultra-precision rifle cartridge was created for snipers and marksmen throughout all five branches of the U.S. military. It’s also adopted by special weapons and tactics teams both domestically and abroad. 

Read on to learn everything you ever wanted to know about the Mk 248 Mod 1 cartridge. 

What is the MK 248 Mod 1 Cartridge?

The Mk 248 Mod 1 is actually a modified variant of the world-famous .300 win mag cartridge. The .300 WM was released all the way back in 1963, along with several other Winchester Magnum cartridges. The round was loaded into a “short” case, meaning that it could function with standard length actions like the 30-06. The .284 WM was released by Weatherby the same year, but never gained traction with consumers.

The .300 win mag was designed to be used in the Model 70 rifle. Manufacturers created the .300 WM by modifying the .338 cartridge. Winchester found a winning formula by making the cartridge available in popular rifles. Such as their own Model 70 and the Remington Model 700. As a result of this wise developmental decision, the cartridge quickly outpaced other rounds being manufactured at the time, such as .300 H&H Magnum.

Adoption by the U.S. Military

Over the next two decades, the .300 win mag continued to gain notoriety among civil shooters, particularly in the hunting community. The .300 WM cartridge offers excellent stopping power and ballistics. With it, hunters could put down big game from a distance. This was thanks to the combination of a relatively level flight path, exceptional muzzle velocity, and heavy projectile.

Despite its commercial success, the .300 win mag did not catch the eye of military decision-makers until the 1980s. At that time, the Navy was actively researching how to improve their weapons systems for sniper and match competition use. They were particularly interested in the .300 win mag for several reasons. Various manufacturers were already producing the round in large quantities, and it had proven itself in civilian shooting competitions.

A Bumpy Start

The Navy held an open competition to determine who would manufacture their new rifle cartridge. They informed participants of the requirements. The average extreme spread of the cartridge could not exceed 8” at a distance of 600 yards. They also required the designers to incorporate a full metal jacket bullet with a weight between 180-190 grains. Lastly, the Navy specified that the cartridge must adhere to SAAMI chamber pressure limits of 68,000-71,000 PSI.

SAAMI or the Sporting Arms and Ammunition Manufacturers’ Institute creates industry standards for the firearms industry. They were founded in 1926 at the request of government officials.

The Navy awarded the first contract to Federal Cartridge Co. in 1987. They incorporated a 180 grain Sierra MatchKing bullet into their winning design. Unfortunately, the Navy’s Judge Advocate General (JAG) determined that the bullet was not suitable for combat use. This was because it had an open-tip design. Federal began burnishing the tips to give it a closed appearance, but this negatively impacted the ballistics.

Various manufacturers put their own spin on the cartridge over the next three years. During one attempt at resolving the design issues, manufacturers replaced the 180 grain Sierra MatchKing with a Lapua 185 grain projectile. However, manufacturers continued to revisit the design strategies.

Ultimately, due to ballistics, the military decided to make the switch back to a Sierra MatchKing projectile. This time, they selected a 190-grain HPBT (hollow point boat tail) bullet. The latest design was in use by both the Navy and Army shortly after 1990, thus the Mk 248 Mod 0 was born. 

Mk248 Mod 0 vs Mod 1

Since its adoption, the Mk248 Mod 0 was primarily used in conjunction with the M24 weapon system. This platform is the military variant of the Remington Model 700 rifle. While an expert marksman can make lethal shots in excess of 1,200 yds (the Mk248 Mod 0’s listed effective range), the military wanted to improve the range of this cartridge. They also wanted to reduce the amount of muzzle flash produced by the round and decrease wind deflection.

During the quest to improve upon the Mk248 Mod 0, military experts examined several cartridges. Manufacturers developed cartridges using much heavier bullets, such as a 250-grain projectile chambered in .338 Lapua Magnum.

However, they ultimately decided to stick with the .300 win mag. The new cartridge incorporated a 220-grain Sierra MatchKing HPBT projectile. It experienced much less wind drift and had a longer effective range than Mod 0. The Army dubbed this ammunition the Mk 248 Mod 1 and began deploying it in 2010-2011.

Who Manufactures Mk248 Mod 1 Cartridges?

Once again, the military awarded Federal the initial contract to produce their new ammunition. However, they changed manufacturers in 2020. Sig Sauer acquired a $10M contract to produce Mk 248 Mod1 cartridges for the U.S. Army. Army personnel will use this cartridge in the M2020 Enhanced Sniper Rifle. 

Can Civilians Purchase Mk248 Mod1?

Currently, the Mk 248 Mod 1 cartridge is unavailable to civilians. This is because the round significantly exceeds SAAMI pressure specifications. If paired with standard rifle systems, the round could damage the barrel and other components. In a worst-case scenario, the excess pressure could cause the chamber to explode, thereby endangering the shooter.

Fortunately, you can get your hands on some top-quality .300 win mag cartridges that will perform great in virtually any distance shooting scenario. Several reputable ammunition manufacturers sell .300 win mag cartridges that closely resemble the Mk 248 Mod 0. This list of manufacturers includes Sig Sauer and Federal. 

You can also purchase hand-loaded 220-grain ammunition that is chambered in .300 win mag. However, I wouldn’t recommend it as the consistency and quality of these cartridges can vary greatly. If you are the unlucky recipient of a “hot” round, you could damage your rifle. Or worse, find yourself missing a few digits when you leave the range.

If you’re looking for the best .300 Win Mag ammo for your rifle, we’ve got a helpful article ready for you on the Widener’s blog!