300 Winchester Magnum is one caliber that has gained reverence and respect over the last 60-70 years. It’s not a new caliber yet has been gaining popularity in the last decade for its impressive velocities and range which made it a popular cartridge when it was first developed. With a strong heritage tied to military use, the 300 Win Mag is a caliber that doesn’t seem to be going away for a while.
30 Winchester Magnum is manufactured by many companies. Shown here is Peterson Match, Long, and Hornady.
Despite so much history and development, for the average shooter, it’s a bit of a mystery and intimidating caliber. The respect is well earned, with an average of over 3000 ft/s and 1600 ft-lbs of force at 500 yards the caliber is one of the larger and stronger commonly used hunting cartridges. By comparison, 30/06 usually trails in velocity and energy by 300.
While they are the same caliber, the brass will vary slightly between manufacturers.
What is the 300 Win Mag and what is it compared to?
Introduced in 1963 for big game and longer-distance hunting. It’s made to fit into a long action receiver which, at the time, was dominated by the 30/06. However, it was shorter than other alternatives like the 300 H&H while still offering similar velocities. Winchester also seemed to compete with Weatherby, which had a comparable 300 Weatherby Magnum released about 20 years before Winchester. In effect, Winchester reinvented the wheel, producing a caliber that was eerily like competitors’ offerings but fit into a shorter receiver.
Note: Winchester “Short” calibers are different but at the time the 300 Win Mag was released, it was considered a ‘short’ caliber.
All these calibers can accept and fire the same 30 caliber projectile. From left to right: 308, 30/06, 300WM, 7.5×55 Swiss, 30/30, 300AAC.
Originally for hunting, the 300 Win Mag became very popular for several reasons:
308 had been released only 10 years prior and was considered somewhat of an anemic, yet capable, cartridge for big game. The military had taken the 308 and developed the 7.62×51 two years later proving it was acceptable for military use. Across most of the Western world, the 762NATO is still the caliber of choice due to its range and energy. But the 308, based on the 30/06, was not quite powerful enough and the 30/06 was still a common hunting rifle due to the abundance of military surplus rifles.
Winchester’s caliber lists were heavily inspired by American’s fondness for hunting. While similar calibers were invented by Weatherby; Norma and Holland & Holland were manufacturers from across the pond with European leanings. So, Winchester kept with their tradition of manufacturing a uniquely American cartridge for the American consumer while competing with the aging Weatherby cartridge.
Because of the popularity of American military arms, the 300WM gained new followers during the war on terror. Beginning in the late 1980s, the US government looked at the 300 Win Mag as an alternative to both 762NATO and 30/06 for their sniper rifles. At the time the M21/M39 (M14), M24/M40 (Remington 700), Winchester 70, M1C (M1 Garand), and M1903 were all commonly found sniper rifles across the branches; with the M1903 and M1C rarely seen in use. Calibers ranged from 30/06, 7 Remington Magnum, and 762NATO.
Advancements in ballistics and metallurgy pushed the U.S. Government to look at alternatives that could punch through armor and reach longer effective ranges. Development, through several growing pains and variations, proved successful with the introduction of the M2010, a long-action Remington rifle based on the M40 platform. This saved the government money by utilizing the M40’s long action compared to the M24’s short action. By 2011, the military had integrated the 300 Win Mag into service.
Besides the obvious range and energy benefits, the 300 Win Mag is a great cartridge for the American hand loader:
It utilizes the same projectile diameter as the 308, 30/30, 30/06, and 300 AAC. All of these are common calibers with different and unique applications. 300 Win Mag extends the usable range of preexisting projectiles for hunting and defensive use. For example, 30/30 commonly utilizes a cast 150-grain projectile (Lee C309-150-F) which can also be loaded into the 300 Win Mag. Utilizing Unique powder, hand loaders can see up to 1372 fps in the 30/30 and 2393 in the 300 WM. In comparison, a 170-gr jacketed projectile can be loaded into a 300 WM using N560 for up to 3048 FPS, 30/03 using N140 for up to 2002 FPS, 308 using N550 up to 2772 FPS, 30/06 using N160 for up to 2799 FPS, and 300 AAC for various super and subsonic loads. Along with these commonly used calibers alternatives like 300 Savage, 30/40 Krag, 300 H&H, and 300 Weatherby Mag utilize the same projectile.
Different manufacturers will carry and offer a variation of projectile weights and points depending on intended use. Pictured is Hornady and MidSouth Shooters Supply options.
But 300 WM brass costs significantly less than these calibers and is easier to find new or once fired. Hornady, Peterson, and Lapua produce brass frequently, and some manufacturers are required to fulfill NATO-caliber production needs. During times of crisis, like the COVID-19 epidemic, when manufacturing plants stopped production of unique calibers NATO cartridges were continually produced. Likewise, barrels, bolts, and other components are manufactured to fit the needs of military service while citizens can benefit from overstock and popularity-pushing production.
That’s not to say the 300 Winchester doesn’t come with disadvantages for hand loaders:
The largest disadvantage of handloading is cost. With popularity comes demand. When everyone wants the same projectiles for a wide range of calibers there are stock issues. Shelves quickly become bare when everyone wants the same projectiles. When demand rises, so does the price. The same applies to cases.
I’d dare say that price is the only major deterrent to 300 Win Mag as a whole. Factory ammunition is expensive, but so is the brass and powder used. Larger case capacity requires the use of more powder for effective loads and powder is not cheap. Using 75+ grains of powder means a single pound of powder can only produce 93 rounds. That’s not accounting for accidental loss and spillage. In comparison, 308 uses 40% less powder and can produce 155 rounds with a 45-grain charge using the same, or similar, powder. Brass itself is uncommon and quality brass, capable of handling multiple reloads, generates a high bill. Hornady brass runs anywhere from $0.72 on sale to $1.40 per cartridge while Peterson averages $150 per cartridge and Lapua costs nearly $2.02 per cartridge at the date of writing. Even on the secondary market brass cases running 75 cents per are a bargain.
Peterson has designed a unique 300 WM case called 300 WM ‘long’ featuring and improved neck and shoulder for specific shooting applications.
With a premium precision caliber next largest expense is time and the tooling required. Precision loads are generally not produced on a progressive press. Quality and solid single-stage presses are a necessity. Since most of the rounds are also fired from bolt action rifles, neck tension often takes priority over crimping, which requires specialty dies and bushings. What is also different from many other calibers is the difficulty in full-length sizing of belted cartridges. It’s not as simple as 308 or even 338 Lapua when using once-fired or range-pickup brass.
That leads me to the last disadvantage, which ails all belted magnums. Quickly, the cartridge will begin to bulge just above the belt and can’t be completely reduced even with full-length sizing. A hand loader will only be able to get 3 to 4 reloads after being formed and neck-sized before the cartridge will not seat fully in the chamber. Collet dies do assist and are the only available option that doesn’t push excess brass inward and toward the rear, potentially affecting headspace. A good trick is to use a collet die to resize and then use a full-length sizing die afterward. This will reduce the bulge over the belt and provide enough sizing on the case body and neck to last for another few reloads. Combine with proper cleaning and annealing for longer-lasting cartridges.
If you load more than just 300 WM, Peterson Cartridge manufactures many other unique cases in common 30 caliber chamberings.
Perfecting the hand load may mean buying quality factory ammunition:
Because of the expense attributed to 300WM, ladder and jump testing isn’t the most economical testing process. Instead, purchasing some high-quality factory ammunition may yield the results, and brass, you need. After firing several grain weights appropriate for your barrel twist rate, stack up the best-performing ammunition. Companies that produce their own load data books (Hornady and Lapua) often load their ammunition to the same, or similar, specifications. By testing several ammunition types from the factory, you have a good baseline for your handloads.
Make 300 Winchester Magnum work for you:
Precision magnum calibers are daunting to begin handloading. There is so much that can go wrong, but when successful they outperform alternative rifle cartridges. The 300 Win Mag has benefits that are hard to beat, like projectile availability and adaptability – which has strengthened my love of 30 caliber cartridges. The versatility and availability of 30 cal ammunition also leave a gap in more common calibers for long-range ballistics, which 300 Win Mag fills. A small group of projectiles can handle everything from subsonic use, hunting loads, defensive ammunition, and long-range precision. With the right loads in the right rifle, the 300 Win Mag can handle ranges up to 1700 yards for precision. While 30/06 and 308 struggle to be accurate at 1000 yards the 300 Win Mag proves that the same projectile just needs a bit more of a push.
