The 300 Winchester Magnum is one of the more useful and effective all-around cartridges in existence. In 1956, Winchester introduced the 458 Winchester Magnum with a case length of 2.500 inches. This was the first true commercial short magnum from a major manufacturer, as it would function in standard-length actions. Of course, there came even shorter magnums in later years, able to function in short actions because they were no longer than a typical 308 Winchester loaded round. Prior to the 458, magnum-length cartridges mostly required a magnum-length action. That's because the 375 H&H Magnum pretty much started the magazine-rifle magnum movement way back in 1912, with a cartridge case length of 2.850 inches. The 300 H&H followed in 1925, and the two cartridges became the basis of the multiple magnum cartridge developments by Roy Weatherby beginning in the early 1940s. Weatherby's 300 Magnum was simply the 300 H&H fire formed in Weatherby's chamber. Same for the 375 H&H being formed into the 375 Weatherby. Weatherby's other early developments, such as the 257 Weatherby Magnum, The 270 Weatherby Magnum, and the 7mm Weatherby Magnum, required additional work such as shortening the case and necking it down. Early on, this was all done by using 300 H&H cartridge cases. The shortening of cases from 2.850 inches to 2.549 inches, and then producing a new neck and fire forming, took a lot of work and we thank Mr. Weatherby for his efforts. Now, since one guy took it upon himself to show the world how it could be done, the major gun manufacturers decided to follow along. Notice how I avoided the use of the word "copy".
Winchester was the first major commercial firearms manufacturer to jump onto the "shorter" magnum bandwagon started by Weatherby, and the 458 Winchester Magnum was its first effort. Two years later, in 1958, Winchester introduced the 264 Winchester Magnum and 338 Winchester Magnum. It's interesting that all three of these new cartridges used the exact bullet diameter in their designation. At that point, more than a few folks, me among them, waited for Winchester to introduce what we expected would be next, the 308 Winchester Magnum. Didn't happen. Norma Projectilfabrik of Sweden beat them to the punch by introducing the 308 Norma Magnum in 1960, shortly after their surprise announcement of the 358 Norma Magnum. Even though the 308 Norma Magnum was almost exactly the same size as what shooters were expecting with a 30-caliber Winchester Magnum, we waited. And waited. Instead of seeing what was anticipated, we were surprised once again; this time by Remington with its new Model 700 Rifle and 7mm Remington Magnum. Here it was, the same basic case as the three new magnums by Winchester, but with just half a millimeter bigger neck than the 264. (Bullet diameter of the 7mm is .284 inches.)
Okay, they've forgotten about the 30 caliber. We'll make our own. The new Wildcat cartridge was simply the 338 Winchester Magnum case shoved into a custom-made RCBS die that necked it down to accept 30-caliber (.308") bullets. So there. The 30-338, as it was called, shot really good. At the time, there were wonderful 180-grain MatchKing bullets available from Sierra, and this was a match that went together like vinegar on spinach. (That means good; try it.) Of course, there are plenty of additional choices of match bullets readily available today, and several work very well in the 30-338; a cartridge that some shooters, including myself, still use.
Winchester must have been frustrated a time or two along the way. They could have avoided this whole mess by offering a shorter 30-caliber magnum sooner, but their Model 70 was already offered in 300 H&H. Besides, funds may have been stretched to the limit. A new, cheaper-to-produce Model 70 was on the drawing board, which is some evidence of shrinking cash flow. Most of the rest of the firearms lineup was also in a cost-cutting exercise.
Finally, in 1963, the new 300 Winchester Magnum was announced. The round didn't look anything like what we expected, but I ran right out to get my Model 70 as soon as it arrived at Coburn Sport Shop in Waterloo, Iowa. I guess I was more excited about this rifle than I have been for perhaps 95% of my many purchases over several decades. I wasn't disappointed. The rifle needed to have a little "tuning" to get it to shoot reasonable and consistent groups, but and old and savvy gunsmith who knew a lot about rifles led me through that. Today I'm older than he was then, but I think I still fall short in knowledge.
The 300 Winchester Magnum had a longer case (2.620") and shorter neck (0.264") than the 30-338 (2.500" and 0.299", respectively). That, of course, made for more powder capacity, which would be fine if the overall cartridge could be longer. Unfortunately, the overall length for standard actions is maxed-out at 3.340 inches. Therefore, to make the whole thing work, the bullets have to be seated a little farther into the case than what would seem to be ideal, and this takes back some of that space for powder that was gained by making the body longer. It's not a big deal. Ammunition manufacturers make excellent products, and knowledgeable hand loaders work right around the situation. When a customer is choosing a rifle chambered for the 300 Winchester Magnum, I like to determine if he is a candidate for hand loading. If so, the Remington 700 can be an advantageous choice. The magazine is longer and the bolt throw sufficient to allow longer loads than in an action absolutely limited to 3.340 inches. Depending on the ogive (curved forward portion) of the bullet, the reloader may gain as much as 0.200 of an inch, plus or minus a little, in overall cartridge length. In any event, this requires considerable care when developing such a load, and in a cartridge of this size I do not recommend bullet contact with the rifling when chambering a loaded round. In fact, some bullet manufacturers recommend specific minimum distances between the bullet and the rifling. Reloaders MUST follow the guidance provided in the proper loading manual for the bullet selected. Being a cheap guy with a irresponsible attitude can get your butt in trouble in a hurry. Buy the books you need and study them like your life depended on it. It may.
I have found that the 300 Winchester Magnum is very effective in most hunting situations and for most big game with 180-grain bullets of better quality. There are exceptions. It may be the only rifle available for your Alaskan hunt in a bear-infested area. While hunting for moose on that day, consider something along the lines of a 200-grain Trophy Bonded or 220-grain Nosler Partition. Otherwise, 180s are a dandy choice for crackling across vast stretches of ground and hitting with an authoritative smack that can't be matched by lighter 30-caliber or smaller-caliber bullets. The 300 Win Mag, as it is often called, is a big stick. One particular African hunter that I know well is absolutely sold on his Ed Brown 300 Win Mag with 180-grain Barnes TSX bullets for essentially all plains game with the exception of eland. African game has the reputation of being very sturdy, so consider this to be a recommendation at least worth thinking about.