Pardon the cut-and-paste, but this write-up summarizes what I have been saying about WSM's for a while...
What advantages does the 300 WSM offer over the long -established .300 Winchester Magnum or the 300 H&H? Most new cartridges today are just a redesign of the case .... lately, the new wave is shorter and fatter cases. The 300 H&H required a 'magnum length' action, which was more expensive. Then came the 300 Win Mag, which main advantage was that it could be built on a 'standard length' action. Now we have the 300 WSM that utilizes a .308 Winchester sized action. Magnum velocities are now possible in a case that is about half an inch shorter than the 300 Win Mag, but with higher pressure and more bolt thrust. The velocity race has its tariffs ... with it comes higher recoil which could turn you into a flincher, and higher flame temperatures will erode the throat of the barrel much quicker. I expect that the Winchester Short Magnum will win the tug-of-war over Remington's long cased Ultra Magnum, even though the 300 Ultra Magnum is still the fastest - pushing a 180 grainer at 3,250 fps. Remington's Ultra Mag cartridges have not been selling that well - at least not here in Africa or in Europe. Winchester will proliferate the short magnum concept from .223 calibre to .338 calibre!
Let us just review the velocity issue very briefly. When Winchester brought out their 300 Win Mag, they purposely loaded it slightly hotter (180 gr bullet @ 2,950 fps) to make the 300 H&H look 'obsolete' - gaining a mere 70 fps but also at a higher pressure level. For many years, the standard .300 H&H factory load in America listed a 180 grain bullet at 2920 fps, but it was quietly reduced to 2,880 fps. With handloading, the .300 H&H Magnum can easily exceed current factory loadings, if need be, but its superiority really lies in the fact that the longer and heavier 200 and 220 grain bullets can be loaded due to its longer case neck. I do not particularly like calibres which employ cases with sharp shoulders and short necks. The new 300 WSM, has a 35 degree shoulder and the same neck length as the 300 Win Mag.
While the .300 WSM is advertised to produce ballistics virtually identical to the popular .300 Win Mag with 150 and 180 grain bullets fired in a 24" barrel, heavier bullets protrude so far into the powder space of the stubby case, that velocities are reduced compared to standard length magnum cartridges, which limits its versatility to use heavier bullets that are needed for bigger game. The .300 Winchester Short Magnum cartridges are so fat, that the magazine capacity was reduced by one round to hold only 3 rounds. Also its shorter magazine box inhibits the use of longer bullets. The .300 WSM is loaded to higher pressure than the 300 Win Mag to give a similar velocity. To say less powder in a shorter case yields a higher velocity is not quite the full story ... it is higher pressure my friend. So, the "more efficient" short and fat WSM case, is just a bunch of advertising hype. The 300 H&H, with its bigger case, still offers the lowest operating chamber pressure of all the .300 Magnums.
The 300 WSM, smaller case and sharper neck is bound to produce higher pressure - my version of QuickLoad does not list the data on this new calibre and thus I cannot do a calculation. I suspect the pressure to be over 60,000 psi. I much prefer lower pressure rifles as one has a greater margin of safety for any changes in temperature, or components, or propellant or seating depth.
If I am limited to use a 180 grain bullet, I might as well use a 30-06 Spr. I expect a .300 Magnum, with its bigger case and greater powder capacity, to accommodate at least a 200 grainer for that added terminal momentum at longer ranges for bigger game. I regard a 200 gr bullet at 2,750 fps as far superior to a 180 gr bullet at higher velocity, for the hunting of big antelope such as Kudu at long range, as its terminal momentum is higher and combined with the heavier bullet's better sectional density, it will yield a higher Knock-out value (KOV). I gladly sacrifice 0.9" bullet drop for the increased punch! Winchester most powerful load for the 300 H&H was their 220 gr Silvertip bullet at 2,620 fps. Many other bullet makers offer 220 gr bullets for the reloader, such as Woodleigh, Sako, PMP, Hornady, Sierra, Remington, and Nosler. Barnes offers a 200 grainer in X-configuration and a 220 grainer in a monolithic solid - these two bullets are some of the longest bullets in .308" calibre. Also various tests confirm that bullet performance is at its best at about 2,100 fps i.r.o. soft nosed bullets.
It should be noted that the original .375 and .300 H&H Magnums were designed with very sloping shoulders, partly because they were intended for use on dangerous game which makes feeding reliability of primary concern. Also, the case did lend itself better to cordite loading, when cordite was still in use. In contrast, the .300 WSM has a short, fat, sharp shouldered case which in my opinion is better suited for benchrest shooting where the main goal is accuracy, rather than chambering quickly another round on a dangerous animal at close quarters. Both the 300 Win Mag and the 300 H&H has a belted case., but the .300 H&H case has a lot of body taper, with a very sloping 8.5 degree shoulder, and this sleek cartridge feeds very reliably, despite the fact that it has a belt. I have never had a mis-feeding in my 300 H&H, nor did I ever hear or read about a mis-feeding.
Increased accuracy and the fact that lighter rifles can be built on with a .300 WSM, are really the only 2 legs that it can stand on. The ignition of a shorter powder charge, with the flame of the primer going deeper into the case, is said to be better as the burning is more complete. This phenomenon can be seen in the very accurate 6 mm PPC in benchrest competitions, but we must also remember that its much lower recoil makes it much more comfortable to shoot with, when many shots need to be fired. The second point of having a lighter rifle, by virtue of having a lighter action, is dubious on a Magnum rifle, that yields higher recoil as opposed to standard calibres like a 30-06 Spr. Winchester's Model 70 Featherweight rifle, with its 24" barrel, weighs 7.5 lbs - I prefer magnum rifles around 8.5 lbs. All .300 Magnums require a 26" barrel to fully burn all the powder to achieve their full potential. In theory, short actions will give less flexing, which should contribute to better accuracy, but I achieve clover size groupings with my 300 H&H, built on a modified standard Mauser K98 action, with a thumb-cut in the left receiver wall !
Obviously, many different factors contribute to accuracy. In hunting terms, I really do not see any benefit in acquiring a .300 WSM and getting rid of my 'old' 300 H&H - there are no real practical advantages to be had. First time buyers, who are happy to restrict themselves to a 180 gr bullet, may well opt for a WSM as the concept is appealing. Rifle builders though, still use the K98 action mostly, so the "shorter bolt throw" benefit really becomes academic. Mauser actions are still the preferred action for most hunters in Africa. The .300 WSM may come in a nice light weight rifle, with a short action, that handles very well is not disputed. Its accuracy potential may also be greater, but can we say it will be more accurate than a Sako factory rifle with their 75 action, which Sako claim to be the most accurate production rifle, aside from custom built benchrest rifles.
All considered, I still regard the 300 H&H to be superior from a hunting point of view .... it has more than adequate velocity, it can utilize heavy for calibre bullets, its lower pressure will ensure easy case extraction on a hot day and reliable cartridge feeding is non negotiable when the hunting of dangerous game is on the cards. The 300 H&H is also more versatile in bushveld conditions, as 220 gr bullets can be loaded with relative ease, unlike with all the other 300 Magnums.
