Caliber is not the only thing considered in an ARP build. Oftentimes the shooters building them are on a mission to come up with the smallest micro ARP possible.
Yet, size can matter in this situation. A smaller ARP is not automatically or necessarily better. For the purpose of illustration, let’s take a closer look at two common sizes of AR15 pistol uppers, being 5 inch and 7.5 inch uppers, along with their relative advantages and disadvantages.
5 Inch AR Pistol Uppers
It is the case that 5 inch AR pistol uppers are among the smallest commonly available on the market, although there are a few instances in which shorter uppers may be available. All the same, an ARP made with a 5 inch upper will be incredibly compact and hardly larger than most handguns.
There are also numerous advantages arising from the choice of a 5 inch AR pistol upper for your build. Let’s start with the biggest of these, which is the compact size.
Except for a few outliers with smaller barrels, 5 inch AR pistol uppers are among the shortest commercially available uppers for ARP builds. This makes them ideal for close-quarters engagements because they will handle very much like a handgun.
Because of their small size, it is also easier to conceal ARPs made with 5 inch AR pistol uppers. They are easier to conceal and transport even with limited space, which in turn makes them solid options as truck guns or for home defense, including the fact that they handle well in tight spaces.
The low weight of an super-compact micro ARP also means that they are lighter to point and shoot, but this is also yoked to a drawback; the lower mass will not absorb recoil as effectively, and shorter barrels in ARPs, especially paired with a 5.56 chambering, result in a lot of port pop and muzzle jump.
The main advantages of ARPs built with 5 inch barrels is that they will be lighter, easier to conceal, and handle better in tight spaces. But, in the spirit of fairness, there are some drawbacks we should consider here as well.
One is the higher recoil and more dramatic muzzle flip, which have already been broached here. Another is that the shorter barrel will result in lower muzzle velocity and energy than a longer barrel would provide.
But perhaps the biggest detriment of a 5 inch ARP is the short sight radius, which is extremely unforgiving and which can make it very difficult to shoot accurately.
7.5 Inch AR Pistol Uppers
Now let’s take a closer look at 7.5 inch AR pistol uppers, which are obviously longer and heavier than 5 inch uppers.
The longer barrel of an ARP built with a 7.5 inch AR pistol upper gives the bullet more time to accelerate before leaving the muzzle, resulting in higher muzzle velocity and energy, which is the first big advantage.
The higher mass will also help reduce recoil and control muzzle jump; there will also be less muzzle flash and pop because the longer barrel gives the propellant charge to deflagrate within the bore rather than at the muzzle.
The longer sight radius of an ARP built with a 7.5 inch AR pistol upper will also prove considerably more forgiving than the sight radius of a 5 inch barrel, making it easier for most shooters to shoot one accurately.
That more or less covers the advantages, so let’s take a closer look at some of the drawbacks. The obvious one is that the longer barrel will be heavier which will make it harder to conceal the ARP, and which will cost it a little bit in terms of performance in close quarters engagements.
How Barrel Length Impacts Performance: Summarizing
As you can see from this article, the length of an AR15 pistol upper can impact the performance of the build in numerous ways, including:
- Overall weight and handling, especially in close quarters.
- Muzzle velocity and energy.
- Accuracy.
- Expandability, based on the length of the handguard and what attachment points there are.
- Recoil considerations, including muzzle jump.
Keeping this in mind, as well as what has been covered by this post, there are arguments to be made form ARP builds with slightly longer barrels, such as those with 7.5 inch AR pistol uppers, and those with smaller barrels.
Explore AR15 Pistol Uppers Here
Whether you’re here for a 5 or 7.5 AR upper or an AR15 pistol upper in a different size, take a closer look through our full collection and get in touch with us if you have any questions. If you have any questions about performance or compatibility you can contact us at Sales@MCSGearup.com and we will help you out.