Barrel Length
It may seem silly to have an article dedicated to barrel length. Legal implications aside, there are some misunderstandings that we want to dispel before we get further into the deep dive.
What is Barrel Length?
This seems like the dumbest of all questions we could probably ask. But we have seen a lot of blatantly wrong descriptions and diagrams.
Barrel length is the distance between the face of the bolt and muzzle.
From a legality perspective, the barrel length may described as the distance from the bolt face to the farthest fixed point at the muzzle (e.g. the tip of a permanently attached muzzle device). We cover this perspective more in NFA and Prison.
Why is Barrel Length Important?
The most important number to remember is 16.
Anything under 16″ is either a pistol or a short barrel rifle.
Anything 16″ and up is a rifle.
If you don’t already know this, please stop here and go read NFA and Prison.
Barrel length is impactful in a couple of ways.
- It affects the weight of the gun. The longer the barrel, the heavier the gun.
- It determines the portability of the gun. The longer the barrel, the less maneuverable the gun in tight spaces.
- It determines the range of the gun. The longer the barrel, the higher the velocity and the more stable the bullet will be as it flies. Both of these equate to a better long range weapons system.
- It determines the gas system length. The barrel length and gas system length will determine the dwell time of the barrel. Dwell time is important for the functionality of the gas system.
Nominal Barrel Length
Every barrel will have a stated nominal length. For the AR-15, a common length is 16″.
The nominal barrel length is almost definitely not the actual barrel length. For example, one of our standard 5.56 NATO barrels measures 16.24″. A Criterion barrel measures 16.14″. The only thing the nominal length should tell you is that it is at least that long.
So if the stated length is not the actual length, how do we determine the true barrel length?
How to Measure AR Barrel Length
To measure the length of your AR barrel, you will need:
- Barrel
- Bolt
- Wooden Dowel (3/16″ is perfect for .223 caliber)*
* You can also use a cleaning rod, but a wooden dowel close to the bore diameter gives a more precise measurement.
- If your barrel has a non-permanent (i.e. not pinned and welded) muzzle device installed, it is best to remove the device to ensure an accurate measurement.
- With the bolt locked in the barrel extension, insert the dowel or cleaning rod down the bore from the muzzle until it touches the bolt face. Be sure that you are not resting on the ejector instead of the bolt face.
- Mark the dowel or cleaning rod exactly where it emerges from the muzzle.
- Remove the dowel or cleaning rod and measure the length that was inside the bore. This is your true barrel length.
Get Social - Share This Page!
Tell Us What You Think!
Your feedback is really important to us. Our goal is to provide the highest quality content possible to help you on your AR journey. If anything isn’t clear, is missing, is incorrect, or otherwise needs our attention, we greatly appreciate you letting us know. It will help us continuously improve our content for the firearms community.