The 7.62x54r and 300 Win Mag are two cartridges many militaries have used for a long time. They both have the same hunting uses and have pretty similar ballistics. With all of this in common, it only makes sense to compare the two cartridges to see which one is better.
Here is the short answer:
The 300 Win Mag will have more energy, slightly less drop, and slightly less wind drift when compared to the 762x54r. So the 300 Win Mag is basically a better overall cartridge, except when it comes to recoil, in which case the 762x54r has less recoil.
With the short answer out of the way, we can take a closer look at each of the calibers, what their best uses are, and why\when you would want one over the other.
300 Win Mag
The 300 Win Mag is one of the oldest magnum cartridges that uses a standard action. It is a belted cartridge that was introduced in the popular Winchester model 70 and it quickly picked up steam from bench rest shooters and big game hunters.
The 300 Win Mag is used by the US military by snipers. But it also is popular in the civilian market by being used to hunt big game such as elk, deer, moose, and even bison. The 300 Win Mag has a lot of energy which is why it is used by a lot of big game hunters. Its high energy makes it great for hunting the biggest of big game animals in North America.
The biggest downside to the 300 Win Mag is its kick. The 300 Win Mag has, on average, 30 foot-pounds of recoil, which is 10 pounds more than a 30-06 or 20 more foot-pounds when compared to a 308 Winchester or 6.5 Creedmoor. So if you have a lightweight backpacking rifle for backcountry hunting, you may develop a flinch after shooting it too much.
7.62x54r
The 7.62x54r is an old cartridge. It was invented in 1891 by the Russian military. Much like the 300 Win Mag, the 7.62x54r is used by snipers to this day.
The 7.62x54r has high energy up close, but at any range beyond 300 yards, it will start to lose its energy and velocity. The 7.62x54r does have enough energy to kill most big game animals effectively at close range. However, it is not recommended to hunt: Moose, bison, and brown bear, or any of the biggest of big game animals of North America.
The biggest downside to the 7.62x54r is that it is not very available. It is only cambered in a few different rifles, and ammo is somewhat hard to find or is expensive. However, there are Mosin Nagant rifles that are still very common and can be upgraded to make a higher quality rifle.
Which one is better
Now that we have taken a more in-depth look at each caliber, we can see which one is better and when you would want one steel over the other.
If you need a caliber that will kill bigger game animals with ease, then you will want the 300 Win Mag. the 300 Win Mag will have a lot more energy than the 7.62x54r. So if you are going to be going on a moose or elk hunt, you will probably want the 300 Win Mag.
Both calibers will shoot the same ballistics-wise. Both calibers will have about the same trajectory, with the 300 Win Mag having about 3 inches of less drop at 500 yards. And the same is true with wind drift, both of the calibers will shoot pretty much identically.
If you need a more available caliber, you will want the 300 Win Mag. The 300 Win Mag had great commercial success so it is way more popular in the US when compared to the 7.62x54r. If you want to be able to find ammo for your rifle anywhere no matter what, you will want the 300 Win Mag.
If you want a caliber that will work for all deer hunting situations but does not have a ton of recoil, you will want the 762x54r. However, you will have to do more looking for a rifle, more looking for ammo, and you will most likely have to pay more for a 7.62x54r so you will probably be better off looking for a different caliber.
Conclusion
When you compare the 300 Win Mag and 7.62x54r, you are going to want a 300 Win Mag: It is more available, has more energy, has less wind drift, and has less drop. Not to mention that the 7.62x54r is pretty much obsolete in today’s world of calibers. The 7.62x54r is outcompeted and is worse when compared to pretty much any other cartridge in the same class.