How long is a stock AR barrel?
Here is your simple, least hassle, most performance for shortest rifle, off the shelf option. The 16” AR-15 barrel is the commercial industry standard that the 14.5” M4 is for the military. Thanks to the NFA they're different. It would probably be 14.5” if not for that, but the 16” gun is a workhorse in its own right.
20″ AR-15 barrels provide the most consistent performance across the widest variety of loadings. There are plenty of modern specialized loads “optimized” for use in a 16″ barrel, or shorter, but the 20″ length will still do things better for any given loading.
An AR pistol is considered any barrel shorter than 16 inches with an overall length of the gun not to exceed 26 inches. You cannot attach a vertical foregrip to an AR pistol. You can use an angled foregrip or a micro handstop.
You can buy 14.5″ barrels, but for most of us, it would require a muzzle device at least 1.5 inches long, and permanently attached, to meet the legal 16″ minimum.
An adjustable AR-15 stock helps you achieve the perfect fit. With an adjustable stock in place, you can alter your length of pull to accommodate your arm length or clothing. The average length of pull for a standard AR-15 is around 13 inches.
The 20” barrel still propels the round faster, and therefore further, with less drop or wind deflection over the distance than the shorter options. Less deviation from the point of aim and the longest non-specialized effective range are the hallmarks of the 20” barrelled AR-15.
As long as you know your velocity—and your bullet's ballistic coefficient—you can know your trajectory. Longer barrels are not more accurate. If anything, it's quite the opposite. Shorter, stiffer barrels tend to vibrate more consistently and are probably more accurate on average.
A longer barrel generally provides better stability for the bullet as it travels down the barrel. This increased stability can result in improved accuracy, especially at longer distances. The longer barrel also increases the sight radius of the firearm, which refers to the distance between the front and rear sights.
Ar 15 pistols are legal (in most places) but there are some seemingly innocuous things you can do to make it illegal unknowingly. There's a bunch so I'm going to list just the really common ones I've seen. If you attach a vertical forward grip its now an sbr and therefore, illegal unless you get your stamp.
According to the ATF, a stock that can reach your shoulder is not a short stock, which means traditional stocks only are allowed on a rifle or NFA firearm, but not on a pistol.
Can I put a shorter barrel on my AR?
It's not necessarily just that ARs are modular, it's that the modular nature—and the separation of the upper and lower receiver—that means every AR owner can customize their firearm to their specifications, from the barrel length right down to rifle handguard options.
Twenty inches is the length required to make the most out of . 223 Remington and 5.56 NATO loads. The 18-inch options are slightly trimmer, better-balanced rifles.
Barrel Length
The length of a short barrel for either an SBR or an AR pistol can range anywhere from 2” to 15.5”, granted the shorter one would more likely be a single shot custom build.
If the AR-15 is a rifle, then the minimum legal length of the barrel is 16 inches. If it is a pistol, then the length of the barrel is less than 16 inches. Most AR-15 pistol barrels are from 7 inches to 10.5 inches. The muzzle blast for the shorter barrels is somewhat abusive.
In case the LOP turns out to be too long or short, you'll need to know the measurement to determine if your stock should be trimmed or replaced. Most factory rifles have an LOP between 13.00 and 13.75 inches (33.0 and 34.9 cm).
Length of pull is one of the most important aspects when determining whether the firearm will fit you correctly. Determining the correct LOP is crucial to ensure proper eye relief and establish a repeatable shooting position. The standard length on all H-S Precision stocks (and many others) is 13.5 inches.
While prices can vary, a typical AR-15 is worth around $400, but the price range generally falls between $300 on the low end to as high as $1500.
It should be kept in mind that legally, the shortest barrel you can get for an AR is 16″. You might be able to get away with a 14.5″ barrel if you pin a muzzle device on it to make the barrel 16″.
According to the NFA of 1934, barrel length dictates what firearm is considered a rifle, pistol, or “Any Other Weapon.” To satisfy the legal definition of a rifle, a 16-inch barrel is required. When paired with a stock, all-in-all, your rifle should be 26 inches.
The AR-15 is the small block Chevy of firearms. Almost all the parts are easily replaceable and there are multiple manufacturers offering parts for them. Off the top of my head, a barrel is a consumable item lasting around 25,000–30,000 rounds depending on type and quality (and who you ask).
What barrel length do special forces use?
The Mk 18 is a short-barreled variant of the M4 carbine. Chambered in 5.56x45mm NATO and features a 262mm (10.3in) barrel compared to the M4's (14.5in) barrel. It is the weapon of choice for CQB when the maximum engagement distance is expected to be less than 300m.
As far as accuracy, well-constructed, high-end AR-15's are capable of better than half-minute accuracy. Cheap ones can usually be counted on for 2 minute accuracy. Almost all moderately good ones will hang around a minute, maybe slightly over or under. About the same as typical bolt-action rifles.
| Barrel Length | Muzzle Velocity | Max Range |
|---|---|---|
| 18 in | 3050 ft/sec | 500 yards |
| 16 in | 2800 ft/sec | 500 yards |
| 14.5 in | 2750 ft/sec | 300 yards |
| 12.5 in | 2600 ft/sec | 200 yards |
Longer barrel lengths are used to maintain a tighter column of shot, for a longer time period. Longer barrels also tend to give a bit higher velocity to the shot leaving the barrel. This helps the shot to settle and have fewer pellets sling themselves laterally as they exit the barrel.
Military sniper rifles tend to have barrel lengths of 610 mm (24 in) or longer to allow the cartridge propellant to fully burn, reducing the amount of revealing muzzle flash and increasing muzzle velocity. Police sniper rifles may use shorter barrels to improve handling characteristics.
