.300 Magnums

Comparing Two .30 Cal. magnums

Q:  I’m in the market for a .30 magnum,  but can’t decide between  the .300 WSM and the .300 Win. Mag. All the reports I’ve read  concerning the Winchester Short Magnums seem indicate that  shorter and fatter is better, and to endow them with a magical  quality that allows them to outperform cases of larger capacity  like the  .300 Win. Mag. Yet, you have often stated that there’s  no substitute for cubic capacity. Like you I don’t believe in pie  in the sky or the tooth fairy so how can the .300 WSM outperform  the .300 Win. Mag?
Rodney Burrows
A:  I own a Winchester Model 70 .300 WSM.  It’s a good  cartridge  that performs as well as one could expect from its volume and has  some real mechanical advantages over the longer .300 Win. Mag. –  all else being equal. Barrel length may be the same for both  rounds, but Expansion Ratio which is computed by dividing the  volume of the cartridge case by the volume of the barrel bore is  a good measure of efficiency. And it favours the shorter case  which could explain the velocity gained by the .300 WSM.  To  properly compare apples to apples, the maximum chamber pressures  of the two magnums are not much different at 64,000 and 65,000  psi.  With factory loads the .300 WSM shows a 10 fps advantage,  probably due to being loaded to an extra 10,000 psi, but in  reloads with bullets weighing 180gn and more the .300 Win. Mag.  shows a definite edge. Despite claims to the contrary, the  smaller     .300 WSM does not outperform the .300 Win. Mag; how  could it when the latter has superior case capacity? The .300  WSM’s short, fat powder column, however, does give an indication  of better ignition and burn with smaller shot-to-shot and  pressure variations in a more practical lightweight, fast-  handling short-action rifle.




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Nick Harvey

The late Nick Harvey (1931-2024) was one of the world's most experienced and knowledgeable gun writers, a true legend of the business. He wrote about firearms and hunting for about 70 years, published many books and uncounted articles, and travelled the world to hunt and shoot. His reloading manuals are highly sought after, and his knowledge of the subject was unmatched. He was Sporting Shooter's Technical Editor for almost 50 years. His work lives on here as part of his legacy to us all.