Winchester’s enduringly popular short belted magnum, the .300 Win Mag, is still one of the best hunting rounds despite fierce competition from modern rimless .30 magnums.
It is clear that the .300 Winchester Magnum is outperformed by super magnums like the 30 Nosler, .300 Remington Ultra Magnum and .30-378 Weatherby Magnum, but I suspect the .300 Win Mag will remain the most popular of all because it offers a level of performance that appeals to the largest number of hunters and shooters.
In other words, recoil is not objectionable and it carefully balances a blend of power and flat trajectory in a well-balanced rifle of medium weight.
When the .300 Winchester Short Magnum (WSM) came on the scene in 2001 offering .300 Win Mag performance in a short action, many thought it would eclipse the longer cartridge, but it never even came close.
Now we see the rise of cartridges like the more efficient .300 PRC, which is designed to carry heavier, high-BC bullets for longer ranges, but they are yet to knock the venerable .300 Win Mag of its throne.
HISTORY
Winchester introduced the .458 Win Mag in 1956, and the .264 and .338 Magnums came along in 1958. All were based on the .300 H&H belted case, shortened to 2.5” (63.5mm) but with an overall loaded length of 3.34” (84.84mm), allowing them to function in a standard .30-06 length bolt-action. It was clear that Winchester needed a .30 calibre to fill the obvious gap in its line of cartridges.
Fred Huntington, founder of RCBS, had already necked down the .338 Win Mag to .30 calibre in 1958 and although the .30-338 gained a moderate amount of acceptance in the hunting field, most of its successes were gained in long-range target shooting.
Two years later in 1960, the Swedish munitions company AB Norma Projektilfabrik entered the market with the .308 Norma Magnum, which was ballistically identical to the .30-338, but varied enough dimensionally so as not to be interchangeable.
Gun-nuts were betting that Winchester would legitimise the .30-338, but got a big surprise when the .300 Win Mag appeared in 1963. It wasn’t a standardised version of the .30-338, but rather something entirely different.
It had a case length of 2.62” (66.55mm), representing an increase of 0.12” (3.05mm) over the .338, but Winchester shifted the shoulder forward about ⅛” (3mm) and gave it a 25-degree angle to increase case capacity. The side-effect of this is that neck length was shortened to .264” (6.71mm).
This resulted in many handloaders unduly criticising the .300 Win Mag, something we’ll discuss later.
Overall loaded length remained the same at 3.34” to allow the new cartridge to fit into a standard .30-06 length bolt-action.
The .300 Win Mag rapidly became very popular, outselling all the other .30 magnums by a large margin. When the .300 Win Mag was developed, the ancient .300 H&H Magnum was the most popular .30 magnum, but Winchester proved it was possible to exceed the oldtimer’s velocities in a more compact package that would fit in a standard-length action.
Although published velocities have varied in recent years, it appeared that the .300 Win Mag could be loaded to 80-120fps higher velocity than either the .300 H&H or the .308 Norma Magnum with the same bullet weight. It lags behind .300 Weatherby Magnum velocities by 100-150fps when both are fired from a 26” barrel with top loads.
HANDLOADING AND BEST BULLET SELECTION
Handloading the .300 Win Mag isn’t difficult but seating some types of bullets in a case with a short neck like this presents problems, though only with certain types of bullets — namely some long-range type bullets. Long-range efficiency demands that a bullet have the highest practical ballistic coefficient, which is to say both sectional density and coefficient of form. This type of bullet is long with a tapering ogive and boat-tail base, and has a relatively short full-diameter mid-section.
Seating this type of bullet in a case with such a short neck presents certain problems. Due to its shortness, the .300 Win Mag’s case neck gets less than the normal amount of grip on the bullet. What’s more, the seating depth of bullets must be adjusted to allow their full diameter shanks to be positioned within the case neck. If seated so deeply that any part of the tapered nose section is inside the case, it will not be held securely against the forces of recoil.
This gives rise to a second problem involving bullet length. Since no more than 0.72” (18.3mm) of the bullet may protrude outside the case (the difference between overall length and case length), it is obvious that the remainder must be inside. If we add the case neck length of 0.264”, we have accounted for 0.984” (25.0mm) of bullet length, but a 180gn Sierra SBT measures 1.292” (32.8mm), and a Sierra 200gn SBT 1.382” (35.1mm). So where does the rest of the bullet go? Obviously, down into the body of the case where it occupies valuable powder space — about ¼” (6mm) of it.
Therefore, it is evident that not all .30-calibre bullets are going to work well in the .300 Win Mag. So the first step in reloading the .300 Win Mag has to be selecting bullets which have the correct dimensional and mechanical characteristics, together with the kind of controlled expansion required for big-game animals.
Fortunately, there’s no shortage of bullets that meet these requirements. The 180gn Speer Grand Slam, measuring only 1.147” (29.1mm) long has a flat base and ample full-diameter section for frictional security. Likewise, Lapua’s 200gn Mega with 1.228” (31.2mm) has less length and longer cylindrical section than the 200gn Sierra SBT of the same weight. Nosler lists 11 bullet choices for the .300 Win Mag weighing from 125 to 220gn.
Evidently, they all have a sufficient amount of purchase to grip the .300 Win Mag’s short neck tightly. Cases for the .300 Win Mag are very strongly constructed and have a thicker-than-usual web to enable them to withstand average chamber pressures of up to 60,000psi.
Capacity of Winchester Super-X cases filled with water to the base of the neck averages 83.5 grains. This is about 4gn more than a .300 H&H case of the same make, and 9.5gn less than .300 Weatherby brass. It is not only the difference in capacity, however, which explains why the .300 Win Mag is unable to fully equal the Weatherby; it also has ⅜” (9.5mm) of freebore.
HEADSPACING: BELT OR SHOULDER?
On a relatively straight case like the .300 Win Mag, the belt can be a nuisance. If the sizing die is adjusted to headspace on the belt, and the chamber is somewhat sloppy, the brass will expand to fill any void between the shoulder of the case and the corresponding point in the chamber. The brass flows forward and the weakest point is just ahead of the belt. That area gets thin and eventually fails. Handloaders might experience case failures in as little as two or three shots. This situation occurs in all bottleneck cases, but is more pronounced in belted magnums.
Many handloaders size their cases by backing off the sizing die one-quarter to one-half turn and locking the ring, which allows the case to headspace on the shoulder. Essentially, the handloader is only partially sizing the case, but I prefer to use a proper neck-sizing die to do the job.
The .300 Win Mag is undeniably a high intensity cartridge, and all that heat, velocity and downrange energy exact a toll. Even if handloaders carefully neck size only, they might see case failures in as few as three or four reloads and have to junk those cases.
In order to take full advantage of the case capacity it’s best to use slower-burning powders such as AR2209, AR2213sc, AR2217 and AR2225. The flatter pressure curves these powders generate allow a bullet to be pushed at near peak pressure for a longer period of time to achieve a slightly higher velocity.
ENDURING FOR GOOD REASONS
The .300 Win Mag then is to Winchester what the 7mm Rem Mag is to Remington. Winchester introduced its .30 magnum in 1963 and it’s been going great ever since. The .300 Win Mag has gained a reputation for being the most useful of all the short belted magnums for North American hunting. Loaded with bullets weighing 165-180gn it has proved to be a superb cartridge for pronghorn antelope, mule deer and elk. With bullets weighing 200, 220, 225 and 250gn, it is effective against the largest moose and bears. It’s been used very successfully on plains game in Africa into the bargain.
As a long-range cartridge it’s also superb, capable of a flat trajectory and landing a heavy bullet on target at 400 metres while retaining enough energy to give good penetration and bullet performance. Recoil is a bit on the heavy side — about 30 percent greater than the .30-06 — but in a properly stocked rifle, it’s nothing that an experienced hunter can’t handle.
Accuracy is another advantage of the .300 Win Mag. In a good sporter it is not at all unusual to get MOA accuracy even with factory loads. Where factory loads are concerned, the 220gn Winchester Silvertip is the heaviest bullet available, but many hunters will choose a tougher bullet, and there are plenty to choose between.
WHY THE 180-GRAINER WINS
I believe that a strongly constructed 175-180gn bullet driven at around 3100fps is the best choice for taking large game such as sambar, moose, eland and suchlike. This means a bullet designed to penetrate deeply and break heavy shoulder bones rather than fragmenting when meeting heavy muscles. The same kind of bullet can easily reach out and drop a deer in open country, which is why the .300 is so versatile.
With today’s strongly structured 180gn bullets, there’s really no need for anything heavier, as the 175-180s penetrate deeper and offer a flatter trajectory over any normal hunting distance. The base of nearly all 180gn bullets protrudes below the base of the neck, taking up some powder space, but does not reduce capacity enough to make a significant difference.
Nor does the .300 Win Mag’s short neck pose a problem anymore. In recent years I have never experienced any bullet movement due to lack of case neck tension. With today’s strong brass and bullets that have the shank properly located to make full contact with the case neck, the problem no longer exists.
There are now any number of bullets that qualify, including Federal’s 175gn Terminal Ascent and High Energy Trophy Bonded Bear Claw, Swift’s A-Frame and Scirocco, and mono-metal designs like the Barnes TTSX, Hornady MonoFlex, Nosler Expansion Tip and Speer Grand Slam. A bullet that provided excellent accuracy for me was the Barnes 180gn MRX BT.
At 1.380” (35mm) long and with a bearing surface nearly ¾” (19mm) long, it groups consistently at 1-1.5 MOA using 72gn of AR2213sc or 76gn of AR2217. I haven’t yet used this bullet on game, but other Barnes bullets in calibres from .257 to .338 have performed perfectly on game for me.
Shooting the Hornady 180gn GMX bullet at 3100fps and zeroing it at 300yd (275m), the bullet hits 3.35” high at 100yd (93mm at 100m), 4” high at 200 and down 9.45” at 400. That’s what I’d call a flat trajectory and then some! The remaining energy at 400yd is 2202ft-lb. This represents a whopping 96 percent increase over the .30-06 and more than double the .308’s energy.
Few cartridges can equal the versatility of the .300 Win Mag. It’s right at home in open country where long shots are common and it can certainly qualify for the title of all-round cartridge. Sure, it’s a bit of overkill for fallow, but it sure does the job well on all of our larger deer species. For overseas hunting, some hunters prefer a larger calibre like the .338, but plenty of moose and brown bears have been taken cleanly with Winchester’s big .30-cal.
Judging by its widespread popularity, the majority of hunters are more than satisfied with its performance.
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