The choices in the AR world can be very overwhelming. You can start by deciding on what you are going to use your AR for. If it is for light use such as home defense or light shooting a standard Mil-Spec barrel is all you need. If you are going to use the firearm in competitions where accuracy and long distances are needed, you will want to go with stainless steel, chromoly vanadium, or a cold hammer-forged barrel.
Here are some things to consider:
The barrel ultimately determines the legality of your firearm. If you are putting it on a rifle the minimum length is 16”. For someone who is building an AR pistol the shortest is 4”. The difference between a rifle and a pistol in the AR world is whether it has a buttstock or brace. A pistol must have a brace and a rifle will have a buttstock.
What does twist rate mean?
The twist rate, or rifling, in a barrel, means the number of rotations per inch the bullet makes before exiting the barrel. So, if you have a barrel that is 1:8 it means that it must travel 8 rotations. The rotations also correlate with the grain of ammunition you are going to use. 1:7-1:8 is good for 69-90 grain, 1:9-1:10 is good for 45-70 grain, 1:12-1:14 is good for 35-50 grain. Most rounds of ammunition for ARs are 77 grain.
Should you buy a barrel with stainless or steel lining?
A chrome lining is used in the military because they are not going to weather in harsh environments. It is also used to protect the barrel from excessive heat, and it is easier to keep clean. But you pay a price in long-range accuracy because chrome is naturally uneven.
A match barrel or stainless steel does not contain a chrome lining. With this, you gain long-range accuracy but have a barrel that is not resistant to high use.
What is the difference in barrel lengths?
The barrel length will determine muzzle velocity and accuracy. If you are shooting close-range targets, you will be fine with a shorter barrel 16”. If you are shooting long-range you will want a barrel that is a little longer in length. The length of the barrel determines blast and velocity.
Should you get a cold hammer or Mil-Spec barrel?
If you are going to use your firearm lightly then you are fine to go with a Mil-Spec barrel, which are typically cheaper. Cold hammer barrels increase long-range accuracy and have a longer lifespan but are typically more expensive.
Why is the profile of the barrel important?
The profile of the barrel is the weight of a barrel, or how thick and thin it is. They can be heavy, lightweight, or government. If a barrel is heavy it will perform for a longer period but ultimately makes the firearm heavier to carry.