By any stretch, a rifle built with a 20 inch AR upper is considered a full-sized platform. It will lack the light, easy handling of a 16 inch carbine, and it certainly won’t be concealable or maneuverable like an ARP.
Still, there is a strong case to be made for AR builds with longer, heavier barrels, and we aim to unpack that here. So let’s take a closer look.
What It Does Well
If you’re considering completing a build with a 20 inch AR upper, there are numerous advantages it will have over rifles with shorter barrels like carbines.
For one, an AR with a 20 inch barrel will be heavier and more stable. Some people prefer this for long-range shooting as well as for hunting.
In the same vein, the longer barrel will add a boost to muzzle velocity, even if you change nothing else. The longer barrel traps expanding gasses for longer, giving the bullet more time to accelerate before it leaves the bore.
That also adds power, so with a longer barrel, you get slightly more muzzle velocity too, even if you change nothing else. For this reason some shooters prefer a longer barrel for sporting applications for hunting.
In the realm of long-range shooting, the extra FPS and muzzle velocity result in a flatter shooting trajectory, so this makes the longer barrel preferable for that discipline. If you’re building an AR for long-range shooting or hunting, a 20 inch AR upper is a good place to start.
Another advantage of a 20 inch AR upper, specifically to shooters that shoot over iron sights, is the longer sight radius. While the rifle itself isn’t strictly speaking more accurate (in fact, a longer barrel may have more complicated harmonics) the longer sight radius will prove more forgiving.
The effect of this is that more shooters can shoot more accurately and more confidently with a longer sight radius, specifically over iron sights.
Reliability is another big thing with a longer barrel, though this is a function of the gas system, specifically. The full length gas system is renowned for its reliability, helping to eliminate issues with jams and other failures. The larger gas system also reduces pressure on the bolt carrier group, resulting in less maintenance and potentially longer-lasting parts.
Also, the added weight of the longer barrel helps increase the static mass of the whole rifle platform, which reduces felt recoil and results in a smoother experience.
What It Doesn’t Do Well
With these benefits of a longer AR barrel having been mentioned, there is a lot that it won’t do as well as a shorter build like a carbine or an ARP.
Notably, a 20-inch AR will be heavier and therefore more taxing to carry and shoot for prolonged periods of time, especially compared to a carbine, an SBR, or an ARP.
Also, a full-sized rifle will not handle as well in close quarters as any of those alternatives. It can still be a practical defensive platform but it will not perform as well in tight spaces.
With that said, an AR with a longer barrel can still be an excellent option for you depending on what you are expecting to get out of the build.
The Short List: When a 20 Inch AR Upper Is a Good Fit
To summarize, here are some of the benefits of an AR rifle with a longer barrel:
- Longer sight radius improves accurate shooting over iron sights.
- Longer barrel adds muzzle velocity and energy, resulting in a faster, flatter shooting bullet.
- The longer gas system is proven reliable.
- The longer gas system potentially drops operating pressure incurring less wear on the bolt carrier group.
- The whole rifle will be heavier, which will help absorb some felt recoil.
At the end of the day, a 20 inch AR upper can be used to complete a full-size rifle that will perform very well for long-range shooting, hunting, and other similar disciplines.
Should You Build a Smaller Rifle or ARP?
If your main goal is to build a rifle that is lighter or handles better in close quarters, then a 20 inch AR upper is probably not the best move for you.
Instead, take a closer look through our collection of AR15 pistol uppers and parts for short barrel rifles and carbine-length builds. These will be better for these applications.
Explore Our Collection of Complete, Assembled Uppers Here
If after reading this you are convinced that a rifle with a longer barrel is the best option for you, start with a 20 inch AR upper or a build kit that has all the parts you need.
Shop our collection of assembled uppers and if you have any questions about parts or compatibility, get in touch with us at Sales@MCSGearup.com and we will be happy to assist.