Loading the 300 Winchester Magnum

Setup For Loading 300 Win Mag

Probably the first commercial 30 caliber magnum was introduced in 1913 AKA the 30 Newton which was ahead of it’s time. In 1925 the 300 H & H came about and was moderately popular until Ben Comfort won the 1000 yard Wimbledon Cup in 1935 after it’s popularity took off. In 1944 Roy Weatherby brought out his 300 Weatherby and for the most part that’s where the commercial market stood until 1963.

That year Winchester brought out the 300 Winchester magnum for their model 70 Rifle. Unlike the earlier 338 mag the case was lengthened and the neck shortened to increase powder capacity while allowing it use in a standard length action.

Right from the start it caught on with the shooting public. Soon most companies were producing rifles and ammo for it. There were some reasons for its popularity. First of all it fit a standard length action unlike the 300 H & H and Weatherby rounds. It was and is very accurate and somewhat versatile. It is very close in power to a 300 Weatherby given the same loads and barrel length in other words it will suffice for almost any animal in North America given proper shot placement and bullet selection. With top loads it will produce two tons of muzzle energy. It also gives a good account of itself in long range matches and sniper work.  Bullets from 110 to 250 grains can be utilized but the heavier ones are better choices for hunting large game. The one drawback is it does kick. It is definitely a step above a 30-06 or 7mm magnum in the recoil department especially with heavy bullets. However if you are experienced with big game rifles you can probably handle it. I have heard that the neck is too short making it hard to hold a bullet but I never experienced that problem and I have shot and loaded a lot of 300 magnum ammo.

Due to its high velocity I would recommend premium bullets for serious hunting chores. If I plan on taking it on a hunting trip I sight in with regular bullets and tweak it with the preemies. I have seen bullets as heavy as 190 grains come unglued on deer and ruin a lot of meat even at ranges of 200 yards or so.

Like all of my firearms I handload over 99% of my ammo though the new factory stuff is pretty good though expensive. Cases, bullets and dies are no problem as the 300 is widespread. The powders should be on the slow side especially with the heavy weight slugs. The powders that I have listed are easily available so I used them. There are other fine powders from Accurate Arms and Norma. Loading techniques are pretty standard though if you want to maximize case life headspace it on the shoulder as opposed to the belt. Set your sizing die so it will chamber but not set back the shoulder. The 300 was designed during a period when some felt that the belts were a necessity to strengthen the case. Time proved that that wasn’t the case. The belt also reduces your magazine by a round. Another good thing about the 300 is you can reduce the loads and still have a useful hunting tool or even a small game round. 

Just to show you that a different brand of primer can make a difference I loaded some up with 74.5 X 7828 and a 200 grain Sierra BT, the only difference was one load used the Rem 9 &1/2 while the other used the FED 215. The Rem clocked at 2896 while the Fed did 2848. Both were accurate but you can see that changing something on your reload can alter the performance. I have demonstrated that on other calibers as well. Also you will notice that I put a few loads with Hodgdon and IMR powders on the same number. The IMR always clocks a little faster and have also done that in other rifles with the same results. 

Reloaders never had it so good. There is a mountain of bullets to select from for any purpose. You can even buy 220 grain solids if desired. Barnes and Hornady make great copper and composite bullets for those zones that don’t allow lead core bullets. Another advantage is the copper bullets are tougher grain for grain then most lead cores. That means that you can go down in weight and still get good penetration on most game. Nosler makes the time honored Partition bullets which always work well. I have always had good results with them. Speer makes that Grand Slam another bullet with a good reputation in the hunting fields. Winchester, Remington and Swift also make good bullets that will stand up to the gaff of the 300. The most accurate bullet in my gun is the 180 grain Sierra BT giving me groups of ½’ when I do my part. I have had a couple of people try and buy my gun when they saw those groups. I would hesitate to use it for hunting except at long range as it tends to come unglued. I have used the Nosler 180 grain to good affect while a good friend of mine uses the 165’s. For less then full loads you can switch to the standard bullets that are used in a 308 and get good results as well as save a few bucks.  

Gun used for these loads is a post 64 model 70 with a 24” barrel. Many people moaned when Winchester did away with the pre 64 but the post shoots just as good and might have a stronger action. For the first few years after 64 it did not look all that good but it was a financial situation that dictated the changes.  I would approach the max loads with caution as each rifle is different and what works in mine might ruin yours. To extend your brass life load your ammo a grain or two below the max loads. The max loads put more stress on the brass usually causing the primer pockets to loosen thus rendering the brass useless. That is true with all rounds not just the 300’s.  Always wear safety glasses and hearing protection when shooting.

After all of these years how good is the 300 Win mag? It will be 50 in a few years.  It’s as good as ever in spite of all the new developments such as the new short magnums. The only magnum more popular is the 7mm Remington mag. Make no mistake they are good but none of short magnums will equal a 300 Win in power given the same barrel length and loads. The old adage still stands, the more powder you can burn the higher the velocity.  With the new bullets all of them will benefit in accuracy and performance. New powders and load development can enhance velocities a little though the value of that might be questioned.

Any of the 300 mags will kill game as far away as most people have any business shooting.  I have shot bear at 40 yards and antelope at 360 yards with it plus other game and distances and never had a problem. I load a 165 grain Nosler Partition for a good friend and he has shot mule deer and antelope some at distances of 400 yards or so and it always does the job. I suspect that as long as rifles exists the 300 Winchester mag will be with us and that’s a good thing.