In the realm of AR tinkering, there are two calibers that get most of the press time. These are .223 and 5.56, far and away.
Past them, a few other popular calibers are .308 and .300 Blackout. These 4 probably get the most builds, with a few others thrown in there.
One up-and-comer that’s new on the scene but might be worth your attention is the .350 Legend.
Before you commit to a build with a .350 Legend AR upper, though, read this.
It’s a Straight Walled Cartridge: Why That’s a Big Deal
With the .350 Legend, the whole thing is about the cartridge’s straight walls (with a little bit to do with its size).
Here’s the thing about straight-walled cartridges. They generally produce lower chamber pressures than similar bottlenecked cartridges.
The end result of this is that they don’t travel as far, and even when they do, they retain less energy downrange than their bottlenecked counterparts.
So, all else being equal, a straight-walled cartridge is not as much of a threat to incidental (accidental) targets downrange as a different, more ballistically-efficient round might be.
Some states have taken note of this and drafted regulations relevant to it. Specifically, states like Indiana, Michigan, and Ohio have enacted new hunting legislation allowing certain straight-walled cartridges for the taking of some game, such as deer.
The idea here is that errant shots won’t continue past the intended target and pose a threat to anyone or anything beyond it.
This is part of the reason for the popularity of some straight-walled cartridges like the .450 Bushmaster, and the entire reason for the development of cartridges like the .350 Legend.
So one of the best reasons to build a rifle with a .350 Legend AR upper is because it is suitable for hunting in states with those regulations in place.
.350 Legend Has Some Advantages in Terms of Defensive Applications
In terms of stopping power, it’s sort of hard to compare .223/5.56 to .350 Legend, but there are some ways to make a fair comparison.
First, we need to talk about sectional density, which is one of the ways ballisticians categorize bullets/cartridges in terms of how much stopping power they produce.
Sectional density, which is a calculation based on the bullet’s weight and diameter, gives a measure of how much penetrating capability it produces. The higher the sectional density, the better the bullet will penetrate a target.
In general, .223/5.56 bullets have higher sectional density scores than .350 Legend bullets, but there is a trade-off here.
Because the .350 Legend produces substantially lower muzzle velocities than the .223/5.56 (in some cases more than 1,000 FPS less), and because it is usually loaded with a bigger, heavier, wider bullet, it produces a large wound channel with less risk of overpenetration.
So while the .223 and 5.56 outperform the .350 Legend at greater ranges, up close, the .350 Legend is a great choice, and one that’s excellent for hunting medium and small game as well.
The .350 Legend Produces Very Mild Recoil
In the spirit of fairness, we need to say this right out of the gate. The .350 Legend produces more felt recoil than .223. We are not suggesting anything otherwise.
Alright, now with that out of the way, let’s try our hand at relativity. The .223 produces (usually) about 4 ft-lbs or so of felt recoil, once you cancel out what gets captured by the gas system, the buffer weight, and the weight of the rifle itself.
As for the .350 Legend, it usually produces something in the area of 8 ft-lbs of recoil, depending on the same factors (rifle weight, buffer weight, etc.). This sounds like a huge increase, but let’s put it in perspective.
A single gram is not heavy, right? Well, two grams weigh twice as much as a gram. Let’s up the ante. A pound isn’t particularly heavy, yet two pounds are twice as heavy. You see where we’re going here?
Objectively, it’s still not a lot of recoil. Think of it this way. A .308 rifle is probably going to deliver anywhere from 16 to 18 ft-lbs of felt recoil into your shoulder, and that’s still not a hard-recoiling round - yet it’s about twice as much as .350 Legend.
So don’t let the idea recoil turn you off.
Do Not Use It to Build a Long-Range Rifle
We’ve said some pretty positive things about the .350 Legend thus far, but now it’s time to talk about some other truths. Truths that might seem like shortcomings.
The .350 Legend, like the .300 Blackout, is not a good long-range cartridge. Depending on load data, barrel length, and a few other factors, you can expect your .350 Legend shots to drop a little more than 30” at 300 yards.
With .223, you’ll experience a drop of less than a third of that, just a bit more than 8” at the same distance.
It doesn’t droop as badly as some other similar cartridges, but it still does not make a good long-distance cartridge, and that is, after all, most of its appeal - relatively poor ballistic coefficient that makes it “safer” to use when hunting in populated areas.
It Might Be Expensive Unless It Takes Off in Popularity
Here’s one more inconvenient truth about building a rifle with a .350 Legend AR upper. Right now, this is a new cartridge and not a lot of manufacturers load it.
This means two things. It can be hard to find (and so can reloading components) and it can also be expensive. If you only use it for hunting a few times a year, buying a case once a season is no big deal, but if you shoot a lot, it could get expensive.
Either way, that’s something to be aware of - but at the same time, if there’s a straight-walled revolution and it becomes more popular, prices may go down in the future if supply increases.
Building a Rifle with a .350 Legend AR Upper Receiver? Start Here
Thinking about making your rifle with a .350 Legend AR upper? For some midwestern hunters, it might make sense.
Start your build here. We carry complete .350 Legend upper receivers, lower parts kits, and everything else you need to complete the build.