The .300 WinMag Still Holds Its Own

By Mark V. Lonsdale, STTU

The past decade has seen significant developments in .30 caliber and .338 rounds for long range shooting to include: .300 PRC, .300 Norma Magnum, .338 EnABler, and .338 Norma Magnum. But be assured, the venerable .300 WinMag is still a practical and tactical contender with a hard hitting 600 to 1,200 yard capability.

For over 40 years, hunters who wanted one caliber that could take all North American game, up to and including big elk, moose, or grizzlies, opted for the .300 WinMag as a reliable go-to cartridge. Rifles were available in Remington 700, Winchester 70, Ruger M77, Sako, et all; and a wide variety of factory 300 ammunition could be purchased in all 50 states. Reloading components were also cheaper and more readily available than for some of the more exotic cousins.

On the military side of the fence, as far back as the 1990s the US military had known the benefits of .300 WinMag over .308 Win, but were slow to bring it into the mainstream. I recall seeing the German army snipers using the Accuracy International G22 in 300 WinMag in Kosovo in 1999/2000, but US Marines were still using the M40A1 in .308 Winchester. While some US Army M24 Sniper Weapon Systems were produced in 300 WinMag, and the US Navy SEALs made wide use of their 300 WinMags in Iraq and Afghanistan, it wasn’t until recent years that the US Marine Corps made the move to the MK13 Mod7, built on the Stiller’s MK13 action.

20190621 AX-AICS

Clone of the MK13 Mod7, built on a Stiller’s MK13 action, but with a Bartlein heavy Palma barrel. 

As the Training Director for STTU, I had demonstrated the 300 WinMag to Marine Scout-Snipers and Recon in the 1990s where they had all seen the advantages of this harder hitting round. One demonstration was at the USMC Mountain Warfare Training Center (MWTC) high angle sniper course, where the Marine snipers were able to get consistent first round impacts at 800 to 1,000 meters with my rifle. Shooting at steel silhouettes also evidenced just how hard the 190 grain SMKs hit in comparison to their lighter .308 Win M40A1s and M40A3s. The most common comment was, “Why don’t we have these?” The staff sergeant running the program was so impressed he went out and purchased his own personal 300 WinMag sniper rifle. But it took the Marines another 20+ years to actually adopt the 300 WinMag.


The STTU .300 WinMag demonstrated to the USMC in the 1990s. This rifle was built by Robar on a Rem 700 action in a McMillan SR90 stock and topped with the Leupold Mark 4 M3 scope calibrated for the 190 SMK 

While newer rounds such as .300 Norma have improved ballistics, the development of the 300 WinMag has not been stagnant. Concurrent to the development of the MK13 Mod7, the US military has also moved from the Sierra 190 SMK bullet in the A191 round to the 220 SMK, designated MK248 Mod 1. The 190 SMK is an excellent 800-1,000-meter round, but the heavier 220 grain SMK carries more energy from 1,000 to 1,500 meters and is less affected by wind.

Not to be out done, Berger Bullets also upgraded their 300 WinMag offerings in recent years with the 185 Juggernaut and 215 Hybrids – both excellent long range bullets. The Berger factory ammo is actually some of the most accurate 300 WinMag we have tested, complete with tight groups, impressive extreme spreads (ES), and low standard deviation (SD).


Federal Gold Medal Match has been the standard by which we evaluate factory ammunition for the past 30+ years, but the Berger factory 300 WinMag in 185 Juggernaut and 215 Hybrid is some of the most consistent ammunition we have ever tested.

For those wanting to build a 300 WinMag, or similar long range rifle, there are several options. Back in the 1990s, before the arrival of the current high quality custom actions such as Stiller’s, BAT, and JJ Rock, we would go to a gun show or pawn shop and buy a cheap long action Remington 700 with a 0.532” magnum bolt face. After tossing the factory stock and barrel, we would replace them with a heavy match-grade barrel and a McMillan fiberglass stock, then true and glass-bed the action.

Note: The 300 WinMag has a 0.532” bolt face, as with the 7mm RemMag, .338 WinMag, and the parent cartridge, .375 H&H Magnum. The Hornady .300 PRC can also be built on a 0.532” bolt face, but a .300 Norma Magnum requires a larger 0.588” Lapua bolt face. The .338 Norma Magnum and .338 Lapua Magnum also use the 0.588” bolt face, as found on Stiller’s TAC338 action.  

But by the time you pay a gunsmith to true and blueprint a stock Rem 700 action, it may be cheaper to invest in a modern custom action. From experience, we can recommend building on Stiller’s TAC300, Predator, or MK13 actions. Stiller’s Actions, out of Garland, TX, won the US Navy and USMC contracts in big part because of the quality of their actions and 100% interchangeability of parts.


STTU .300 WinMag built on Rem 700 Long Action with a Bartlein Heavy Palma barrel, in a McMillan A6 stock, with Badger Ordnance M5 bottom metal and an Accu-Tac bipod. 

For the long range shooter, whichever route chosen, the heavier bullets available for the 300 WinMag will hit harder and have less wind deflection in the 800 to 1,500-yard range. The bullets we’ve had success with include the 190 SMK, Berger 185 Juggernaut, 215 Hybrid, 210 SMK, and 220 SMK. These are all match bullets but there is also a wide variety of bullets from Berger, Sierra, Barnes and Hornady more suited to hunting.

For aspiring extreme long range (ELR) shooters, to dominate at 1,500 and push out to 2,000 yards, then .338 Lapua or .338 Norma are better choices. The .338, running 275 grain to 300 grain bullets, is a good entry level caliber, but if the goal is to push out passed 2,000 yards, then a .375 CheyTac or similar is a better option. Even with a heavy 30-inch barrel, the .375s can be built to a total weight of 24 pounds, permitting the rifle to be run in the under 25-pound class.


Hill Country .375 CheyTac in the rear (24 pounds) and .338 Lapua Magnum in front (16.5 pounds). Both rifles are built on Stiller’s Actions, Bartlein barrels, McMillan A5 stocks, Accu-Tac bipods, topped with NightForce ATACR 7-35x56mm FFP scopes.

To wrap this up, if you have an old 300 WinMag in the back of your safe, or any magnum action with a 0.532” bolt face, this may be the time to invest in a new Bartlein barrel and McMillan stock to really extend the legs of your rifle. Practicing with a 300 WinMag is also significantly more affordable than feeding a .338 or .375, plus it saves wear and tear on your ELR rifle barrel.


About Mark V

Dedicated shooter, seeker, traveler, teacher, trainer, educator
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