When you start building an AR-style rifle at home, whether you intend to use it for defensive applications, for hunting, for competition, or just for fun at the range, you will certainly have a lot of details to dig through.
For instance, will you build it with a forged or billet lower? Will you start with a complete lower and a parts kit, or machine your own with an 80% lower? Will you buy a stripped upper and assemble it, or will you buy a complete AR15 upper?
What trigger will you use? What sort of bolt carrier group coating appeals to you? How heavy do you want your buffer weight to be? What caliber?
And so on and so forth.
Another thing you will have to determine before building is what AR15 barrel to choose, in terms of caliber, length, weight, finish, and of course, what material in the first place.
One of the most important considerations you will end up making is what sort of steel (or, in some cases, what other material) you will want for your build. Here’s a quick breakdown of some of the more common alloys.
Carbon Steel Barrels: Different Grades
One broad class of steel is known as “carbon” steel barrels, and, despite the fact that all steels have carbon (they wouldn’t be steel if not) there are still a lot of fine details that must be parsed so you really know what you’re getting.
Here are some of the main “types” of carbon steels used in the production of AR-style rifle barrels.
- 4140: With .4% carbon, 4150 steel is a relatively strong, hard alloy that produces moderately wear-resistant AR barrels. It also contains a bit of chromium and molybdenum, which together help make the steel harder and tougher than conventional carbon steel alloys. Most 4140 barrels are relatively affordable and despite the fact that you wouldn’t call them “match grade” they can still produce a quality rifle.
- 4150: With a smidge more carbon, at .5%, 4150 carbon steel is just a bit higher-quality than 4140. It is harder, stronger, tougher, and more wear resistant by a small margin. However, like 4140, it also contains small amounts of chromium and molybdenum that make the alloy tougher, stronger, and more wear-resistant. Since there is more carbon in these barrels, and the alloy can take a harder heat-treatment, most 4150 barrels will last a little longer than 4140 barrels.
- 4150 CMV: The “CMV” in 4150 CMV standard for chrome-moly (sometimes referred to as chromoly) vanadium, or chrome-moly-vanadium. This is like the 4150 alloy, but has a little vanadium into the mix, which is an exceptionally hard, dense, strong element. This makes 4150 CMV steel barrels harder and stronger than their “regular” 4150 counterparts.
These are only a few of the different types of “carbon” steels used to produce barrels for AR-style rifles, but they are also the most common.
“Stainless” Steel Barrels: Different Grades
In addition to the carbon steel alloys that are used to produce AR rifle barrels, there are also numerous grades of stainless steels that are used for the same purpose and which are sometimes paired with complete upper receivers. These are some of the most common.
- 17-4 PH: Not as common as it was in the early 2000s, 17-4 PH stainless steel is an alloy that can produce a high-quality barrel that offers exceptional resistance to high temperatures.
- 410SS: The “400” series of stainless steel alloys are known as “martensitic” steels and are designed to offer improved machinability, so they are easier to work with although they are not as hard, strong, or wear-resistant as most carbon steel alloys. These barrels tend to be affordable, which can make them attractive, but bear this in mind; extremely cold temperatures can cause barrel failure, so if you live in a very cold climate, consider a different alloy. This one’s probably not for you.
- 416SS: Another martensitic alloy, 416SS contains higher levels of sulfur which also improves machinability, making the steel easier to work with. A lower cost alloy, it also does not exhibit exceptional corrosion-resistance, especially for a “stainless” grade.
- 416R: This is one of the better grades of “stainless” steel commonly used in the production of AR rifle barrels, and it exhibits better strength and corrosion-resistance, as well as tolerance to extremely cold temperatures, as low as -40℉. It has a tighter steel grain structure which improves strength and durability, and also is capable of producing a much more inherently accurate barrel than the other grades mentioned in this section. The one tradeoff is that this alloy is more expensive.
Again, this is only a small sampling of the stainless steel alloys used to produce AR barrels, but these are among the most prevalent.
AR15 Uppers: Other Barrel Materials
In addition to steel alloys, AR15 uppers are also sometimes paired with barrels made from other, less conventional, materials.
- Aluminum: Aluminum barrels with steel inserts/sleeves are sometimes used to produce AR barrels for low-pressure cartridges, like .22 LR. This metal has limited utility, however, due to its lower strength and softer nature than steel.
- Titanium: Titanium is about as strong as steel but only half the weight, and harder than aluminum. Still, titanium barrels are usually steel-lined to provide better wear and high-heat resistance.
- Carbon fiber: Some ultralight rifles are made with barrels that have an outer shell of carbon fiber and an inner liner of steel. Carbon fiber is lightweight, yet rigid and strong, making for a great option in some scenarios.
Start Your Build with an AR15 Upper from MCS Gearup
Ready to get started on your AR15 build? MCS Gearup carries everything you need, including stripped and complete AR15 upper receivers with a variety of barrel lengths, lowers and lower parts kits, build kits, and all of the parts you need, piecemeal to assemble a functioning rifle.
This also gives you the flexibility to completely customize your rifle build along the way. Take a look through our collection of AR uppers and lowers, AR15 triggers, charging handles, gas systems, bolt carrier groups, barrels, handguards and rail systems, grips, AR15 sights, and optics, and start customizing today.