Originally, the concept of a large case .30 caliber was to extend the range and flatten trajectory of big game bullets in open plains and mountainous country. Increased killing power on large game seems to have been a secondary consideration.

In the mid-1940s, however, Roy Weatherby had other ideas. If velocities could be raised significantly, he reasoned, a shocking effect such as to increase bullet destructiveness on soft skinned game animals, along with a major disruption of the nervous system, would ensue with a consequent enhancement of killing power.

To accomplish this, he expanded the .300 H&H case, decreasing body taper and designing a double radius shoulder, thereby enlarging its powder capacity. In 24-inch barrels, actual velocity (as opposed to claimed muzzle speed) with 180-grain bullets from the Weatherby case showed a gain of around 300 fps over a .300 H&H, mostly due to a 16 percent increase in the powder charge.

Roy took one of his new rifles to Africa where it proved deadly on large plains game, validating his contention, at least to some degree. Of course, with the higher velocity, trajectories were also flatter, assisting hunters in better shot placement at longer range.

As a result, the .300 Weatherby Magnum attracted big game hunters around the world - and still does. Changes have been made in Weatherby magnum rifles increasing their effectiveness, including a longer standard 26-inch barrel with a steeper rifling twist rate of one in 10 inches rather than the old 24 inches with a one-in-12-inch twist. It is to be expected that variations in barrel length, amount of freebore and rifling twist can and will produce differences in velocity as well as pressures.

This writer’s first .300 Weatherby Mark V was an early one made in West Germany with a 24-inch barrel and 12-inch twist but, for all that, was tremendously effective, taking a bighorn ram and Rocky Mountain goat at long range in the mountains of British Columbia.

So good was it that I acquired another in the 1980s, prior to the change in barrel length and rifling twist. Produced in Japan this one again has a 24-inch barrel. No matter, its quality is every bit as good in all respects, perhaps even some better in stock wood graining and finish. Maybe it just looks that way because it hasn’t been subjected to the rigors of mountain trails like the first one.

Whereas .300 Weatherby rifles and cartridges were originally proprietary, they have in recent years been adopted by other makers - rifles from Winchester, Remington, Sako and Sauer; factory ammunition from Federal, Remington, CCI-Speer and Hornady - moves sure to add to this caliber’s popularity (though not used in these trials).

For almost 50 years the .300 Weatherby Magnum claimed the title of highest velocity .30-caliber commercial cartridge, exceeding the .300 Winchester Magnum and (in my rifles, at least) equaling the ballistics of the big 8mm Remington Magnum.

Recent hunting seasons, however, have witnessed the introduction of several new competing calibers, real barrel burners. Faster than our .300 are Weatherby’s own .30-378, the .300 Pegasus and Lazzeroni’s 7.62 Warbird. We also have the .300 Remington Ultra Mag and .300 Dakota, which are about equal ballistically to a .300 Weatherby with 26-inch barrel.

Considering that a .300 Weatherby with 180-grain spitzer loaded to a muzzle velocity of 3,100 fps and sighted 2.3 inches high at 100 yards will strike only 3 inches low at 300, and 13.7 inches down at 400 yards, it’s a fair question as to who needs anything flatter shooting?

That load delivers 2,908 foot-pounds (ft-lbs) at 200 yards, 2,518 at 300 and 2,167 ft-lbs at 400 yards. By comparison, a full-power .30-06 load with same 180-grain bullet has 2,170 ft-lbs remaining at only 200 yards. Think about those figures for a minute and ask yourself whether you need - or can responsibly use - more long-range performance than that of a .300 Weatherby Magnum?

Those ballistics pretty much explain why this cartridge has been so highly acclaimed as a big game round. If deeper penetration on large, heavy-structured game is wanted, premium controlled expansion bullets of 200 grains are readily available to serve the purpose. Personally, if I felt a need for more power than the .300 Weatherby provides, I’d look to a larger caliber with heavier bullet, rather than seek still higher velocities in a .30 caliber.

With all the negative criticism of belted cases one hears these days, a bit of fresh air is called for. If a shooter will reload only cases initially fired in his own rifle, exercising care when partially resizing not to set case shoulders back from their fireformed location, belted cases will then headspace on their shoulder (as with a rimless cartridge), ignoring the belt. If this is made a standard procedure, belted cases will last longer and give no more trouble than a rimless at equal pressures.

A particularly silly claim in favor of the new big rimless cases over belted brass appeared recently. This fellow was extolling the advantages of new rounds based on the .404 Jeffery rimless case, arguing that they take up less room in the magazine than belted cases. I assume his comparison was to our standard belted cases from .300 magnums to a .458 Winchester.

Somebody please hand that writer a micrometer if he can’t just see that our popular belted cases are smaller rather than larger, even if measured over the belt, than across the base of a .404 or the new magnums based on that large rimless case. Indeed, some rifle builders list magazine capacity as five rounds of .375 H&H Magnum or four rounds of .404. That pretty well says it.

One more note on .300 Weatherby brass: Cases should be checked for length after resizing prior to reloading, since in addition to stretching in firing, some full-length dies will cause further lengthening, though this is less likely to occur if the die is backed off for partial sizing.

Consider 2.825 inches as maximum case length. When found in excess of that, trim back to 2.815 inches or just 2.81 inches, and chamfer case mouths.

In our 1971 test series, Federal 215 Large Rifle Magnum primers were used with complete satisfaction, but this time I wanted to try CCI 250 Large Rifle Magnum caps as they have given such good results in other large cases, again with no problems. Complete ignition of the large loads of slow-burning powders in this long case is necessary to assure uniformity of combustion and accuracy.

Realizing the .300 Weatherby is first and foremost a cartridge for taking large game, the selection of proper bullets is of utmost importance. The question as to a game animal’s size, weight and toughness is, of course, primary but hardly the only consideration. The range at which the shot is likely to be taken and, therefore, the bullet’s remaining velocity and energy likewise places demands on the bullet’s construction.

If bullets are too thinly jacketed, they are apt to disintegrate prematurely, especially if velocity is high and the animal close; too heavily jacketed and it may zip right through without sufficient expansion.

For soft-skinned smaller species, standard softnose bullets of proper weight have done well for me, but when a tough old settler with wide beams or a shaggy bruin is the target, the modern premium big game bullets of controlled expansion are worth their higher cost.

My choice has long included the ever-reliable Nosler Partition bullets, along with Speer’s Grand Slam and Hornady’s InterLock, and I’ve yet to have one of ‘em let me down so will continue to use them. Lately, though, they’ve been joined by the versatile Swift Scirocco .30 calibers. Its newest 165-grain design is stoutly jacketed and a real speedster in the .300 Weatherby, a fine long-range bullet.

Presently, for really big stuff, my choice would be either a Hornady 180-grain Spire Point InterLock or Speer Grand Slam of same weight at longish ranges but, inside 200 yards where deep penetration is sought, would favor Nosler’s 200-grain roundnose Partition. For elk in timber where flat trajectory isn’t needed, a 220-grain roundnose or semispitzer is worthy of consideration.

Freeboring or long throating has the effect of lowering pressures, so if this factor isn’t present in your .300 Weatherby, the better part of valor would be not to exceed my listed maximums!

Now with that cautionary note said, my advice is still to start with loads at least 5 percent below those given here. Better to work up than have to back down. Also, if your barrel is 24 inches, don’t be surprised when velocities fail to equal those obtained from 26-inch barrels, those longer tubes making a considerable difference, especially with very slow-burning powders.

As the fastest burning of the powders in this series, IMR-4350 wasn’t paired with bullets heavier than 180 grains (though usable with all weights) because of its tendency to increase pressures more rapidly as compared to the slower burners, particularly with heavy bullets. Also, while somewhat cleaner burning, accuracy with IMR-4350 didn’t average as small as with the slower burners in our rifle.

IMR-4831 was the first step in our progression toward slower-burning powders and while not greatly different from IMR-4350 with 150- and 165-grain bullets, its action with heavier bullets was noticeable to the extent that it was compatible with even the 200- and 220-grain bullets and is preferable as an all-around powder in the .300 Weatherby, in my view.

Next up is RL-19, about the same degree slower burning than IMR-4831 as the latter differs from IMR-4350. So again I used slightly heavier charges. Seemingly not as popular with most authorities in the .300 Weatherby as its slower sibling RL-22, it is nevertheless a fine powder if not overloaded. Do not exceed our listed loads of RL-19.

With Accurate Arms XMR-3100 we get into the realm of really slow burners, and various barrels will begin to demonstrate an individual preference, one way or the other, as to accuracy and/or velocity. Barrel lengths of 26 inches show the slower burners to best advantage, though XMR-3100 does well in this 24-inch barrel.

My loads of RL-22 are about maximum in the test rifle, registering our highest velocities with 180- and 200-grain bullets, and I’d start a bit lower with another rifle. Even rifles of same make and caliber react differently, as did my earlier .300 Weatherby that had accepted some loads   I decided not to duplicate in this one.

Load levels with RL-22 and Hodgdon’s H-4831 (not its new “Short Cut” H-4831) are much the same, and I must say these two powders appeal to me as being about the best all-around in my rifle, covering all weights of bullets from 150 to 220 grains, enabling a handloader to standardize on a single powder, changing only the loads.

The slowest burning - IMR-7828 - by contrast, was not used with bullets lighter than 180 grains, hence is primarily coupled with heavy bullets where it performs its best.

A favorite all-around .300 Weatherby load? That’s hard to pin down to a single combination of bullet and load, but let me just say - based strictly on my rifle - a 180-grain Speer Grand Slam with 80 grains of either H-4831 or RL-22. In another rifle, I’d try 78-grain loads first before going to 80. This further presumes bullets seated to the overall loaded lengths listed do not contact the rifling origin as that would increase pressures.

Once the handloader has determined which bullet, powder and load functions best in his rifle - and doesn’t exceed allowable pressures for that specific rifle - he should shoot often enough to become accustomed to its recoil. The hunting field is no place to find he’s recoil-shy!

Nor is it the time to discover that handloaded rounds won’t feed from the magazine and chamber readily, so before leaving on a hunt best be sure to run each and every round from the magazine to the chamber.