First let go over the different types of barrel steel and processes used to make the barrel. These will be CMV, Stainless & CHF
Chrome – Moly – Vandium (CMV)
This is the most common type of barrel steel used. It comes in mainly two forms.
4140 – carbon spec. 0.43 – Some say this mat be more thermally stable?
4150 – carbon spec. 0.48 – Some say this may be better for full auto?
Most shooters (even heavy shooters) will never notice a difference between 4140 & 4150 CMV barrels
The US military uses 4150 CMV
Stainles barrels are heavier
They can also be more accurate because the alloy is more maliable and allows for finer precision during the manufacturing process, if manufacturer takes time to do so.
Buy from a respected manufacturer to ensure barrel was precisely made for better accuracy
Cold Hammer Forged (CHF)
Cheaper cost per unit for manufacturer but manufacturing equipment is much more expensive making it harder to profit unless many units are produced and sold, which is why so few companies produce CHF barrels compared to those companies that produce CMV barrels.
CHF barrels are usually chromed lined.
Unlike standard barrel manufacturing, where a barrel blank is placed on a lathe and a machine drills the rifling into the barrel blank, with CHF a barrel blank is placed in a CHF machine and a mandrel with reverse rifling on it is placed in the barrel blank and the machine presses the steel onto the mandrel to press the rifling into the steel.
This process has the potential to make for a more durable and longer lasting barrel if done correctly, otherwise it offers no more barrel longevity than standard manufacturing processes.
Buy from respected manufacturer to get the benefit of a more durable barrel. FN is the manufacturer of choice for many shooters as they manufacture this same barrel for the US military.
Chrome Lined vs Non-Chrome Lined
Chrome lined barrels tend to be better at extraction and corrosion resistance and cleaning but tend to be slightly less accurate than standard non-chrome lined barrels, but this difference is so nominal that most users will never notice a difference.
If there is a difference it is probably more likely due to poor manufacturing than the chrome lining.
If you’ll be shooting steel cased or dirty ammo often chrome lining might be a better option for you, otherwise it really makes no difference and chrome lining is more expensive (by about $50 to $75 for a barrel), so if you don’t plan on shooting that type of ammo don’t waste the extra money.
Barrel Twist Rate
The barrel twist rate basically means how many complete revolutions does the rifling make inside the barrel.
For example a 1:7 twist rate means that every 7 inches the rifling makes one complete revolution around the inside of the barrel. So the smaller the second number, the faster the rifling spins the bullet.
The most popular are 1:7 and 1:9 (although a newer 1:8 twist rate is becoming more popular).
Basically the twist rate breaks down like this – the heavier/longer the bullet is the more spin is needed to stabalize that bullet, so for instance a 62gr 5.56 would have much better accuracy and range out of a 1:7 twist barrel than a 1:9.
The best overall twist rate will be 1:7 because it’s accurate with the widest range of bullet weights and lengths (although some people claim that a 55gr bullet can be overstablized in a 1:7 twist barrel and loose some accuracy, the percieved accuracy loss is still negligable and most shooters wouldn’t notice a difference)
All in all 1:7 is going to be your best bet although it can be slightly more expensive, it is fast becoming the industry standard. However if all u plan on shooting is 55gr loads then you might be better served just getting a 1:9 twist and saving a little money.
Chambering is pretty simple, make sure your barrel is chambered for 5.56mm ammo.
This allows you to fire either 5.56x45mm ammo or the cheaper .223 ammo.
If you purchase a .223 barrel you should not fire 5.56 ammo out of it.
Most AR barrels are 5.56 but there are still a few manufacturers out there making .223 only rifles, so be aware.
There are many options for barrel lengths, 8.5″ – 10.25″ – 11.5″ – 14.5″ – 16″ – 18″ – 20″ and a several others.
We’ll only be discussing the most popular lengths 14.5″ – 16″ – 20″
16″ is the most popular as is suites most types of shooting including long range, CQB, defensive shooting & just having fun at the range.
14.5″ is basically the same in function and purpose as the 16″ except due to laws a 1.5″ muzzle device must be permanantly attached to the barrel to ensure the length is at least the 16″ legal limit
20″ is usually religated to longer range shooting and range use and generally considered to be less desirable for CQB or defensive situations where a shorter barrel would be more useful.
Your standard barrel contours are Lightweight (pencil) Barrel – M4 Contour (government profile) Barrel – Heavy Barrel – and many other barrel designs, many of which are custom or fluted designs that each offer their own unique advantage and disadvantages. We’ll discuss the most popular.
Lightweight (pencil) barrel is very popular for a lighweight easily manuverable rifle design. If your doing a lightweight build this might work for you, but keep in mind that it does have a shorter life than other barrels and should not be choosen if your a heavy shooter who puts alot of rounds through your rifle.
M4 contour (government profile) is pretty much the standard in most carbine length rifles. It offers good weight with good barrel life. Great for most shooters.
Heavy Barrel is a considerably (in barrel terms) thicker barrel adding life and heat resistance to your barrel but it does so in exchange for more weight.
So thats it, the basics of AR15 barrels. Hopefully this article will hep you in choosing a barrel for your next AR purchase or build.