You don’t need to read it here to know that 5.56 is probably the most common AR chambering, not just for full-size rifles and carbines, but also for ARPs.
It is cheap, produces little recoil, accurate and reliable (even at long ranges) and has sporting applications too, such as for competition shooting and hunting.
But it does lack on other fronts, which is why you probably landed here, wondering if a 7.62x39 upper might be a better choice for you.
The 7.62x39mm cartridge, also known as the 7.62 Soviet, is the cartridge around which the AK-47 and SKS rifles were chambered, and it has a long history of military and civilian use.
In some ways it’s similar to 5.56, in other ways, not so much. Let’s put them head to head.
Availability
This is one area in which the 5.56 and 7.62 Soviet are basically on even footing. The 5.56 is loaded for our military, as well as for civilian shooters. The 7.62 has been loaded for other militaries and is widely marketed to civilian shooters as well. Pretty much any gun shop should have these in stock, and plenty of options to choose from. Most shops should also have surplus and bulk deals, too, which brings up the point of price.
Price
There was a time when bulk, steel-cased ammo was actually cheaper than 5.56, but in the past few years, that has flipped. Now comparable 5.56 and 7.62 rounds are actually comparable in price, and in some cases, 5.56 might even be cheaper. Unless that changes you can expect them to remain fairly equal on this front.
Recoil
The 5.56 produces less recoil than the 7.62, but with a rifle or even a carbine, it’s not going to be a big difference. Plus, you can tweak the gas system or the weights in the buffer tube system to help manage that. It would be more of a difference in an ARP; if you build an ARP with a 7.62x39 upper, expect it to produce a good bit more recoil.
Size, Weight, Compactness
These are both intermediate cartridges, so they are really not that far off in dimensions. The 7.62 is however bigger and heavier, and since it isn’t as compact, you can carry as much of it in the same space or as economically. That would only really matter if you were carrying around hundreds of rounds, though.
Performance from a Shorter Barrel
The 5.56 will perform very well from rifle and carbine-length barrels, but in ARPs, usually the whole powder charge doesn’t fully deflagrate. That means a few things.
One is you get less power from 5.56 through a shorter barrel. The other is that there is a lot of muzzle pop, and on top of that, the whole rifle will be dirtier, and there will be more fouling.
The 7.62 Soviet performs better through shorter barrels, which makes it a good pairing with short barrel uppers as well as AR15 pistol uppers.
Stopping Power
The 5.56 does not produce as much stopping power as 7.62 Soviet, which makes the latter a much better defensive cartridge, especially at close ranges.
Your typical 5.56 round will produce between 1200 and 1350 ft-lbs of muzzle energy, compared to a range of roughly 1500 to 1600 ft-lbs for the 7.62 Soviet.
In other words, a rifle built with a 7.62x39mm upper will produce significantly more stopping power and will be better situated to stop threats at close ranges.
Performance at Range
The one thing a rifle with a 7.62x39mm upper will do poorly, regardless of barrel length, is shoot accurately at long ranges.
The expression “drop like a rock in a sock” has been used to describe the performance of cartridges like these, and it is unfortunately accurate (unlike 7.62 Soviet at long ranges).
That is to say, this round’s trajectory droops terribly at ranges in excess of 100, perhaps 200 yards, making it really only effective at ranges closer than that.
Consider a .300 BLK Upper Instead
Another alternative to a 7.62x39mm upper which will produce the same basic advantages covered here is a .300 BLK upper.
Like 7.62 Soviet, .300 BLK produces more stopping power than 5.56 and performs well from a short barrel. It also has a badly drooping trajectory, making it less suitable at long ranges.
However, it is harder to find and it is more expensive, but one advantage is that if you get a .300 Blackout AR upper, you can use the majority of 5.56 parts with it; they even can accept the same bolt carrier group.
Don’t Decide Right Now: Explore Both 5.56 and 7.62x39 Uppers
You don’t need to make a decision this instant about whether you’d be better served by either a 5.56 or 7.62 Soviet build. Explore our collection of 5.56 and 7.62x39 uppers in both rifle and AR pistol lengths, and get in touch with us at Sales@MCSGearup.com if you have any questions.