Let’s Talk Barrel Materials & Coatings
By Nate Dawg
So, on today’s rant you are going to read about barrel materials and why it’s one of the 5ish things you should look for in a rifle. This is for sure the most important when it comes to accuracy. If I can give you one piece of advice when shopping for your next AR is that every tool is made for a specific reason. Just because the military uses it in combat doesn’t always mean it’s the best material for you. So please enjoy. There is no better or best, just what is right for your use. I’m not going to get super nerdy here. This is more about purpose than chemical composition.
CMV (Chrome Moly Vanadium)
So, there are types of carbon steel. They are 4140 and 4150 and the difference is the tensile strength. 4140 is around 95,000 PSI and 4150 is around 105,000 PSI. Considering a 5.56 round is only around 62,000 Psi you are good to go. Ok that’s the only part ill nerd out because people get caught in that loop all the time. Since these are carbon-based barrels, they need to be coated to protect them from rust.
That’s kind of where we get into Vanadium. What is Vanadium? It’s a thing they add to 4150 steel to give them a higher tensile strength and less susceptible to rust due to an oxide layer forming. Some say that they don’t need to be coated but in my opinion that is wrong. Everything should be coated. It adds life to it and other things we will get into later.
The benefit to this barrel type is it has longer barrel life and carbon steel handles heat better than the other materials. What you give up for this a lot of time is accuracy. This is because the hardness of the material makes it more difficult to create the rifling. I think CMV is mil spec, and the mil spec is 4 MOA at 100 yards, so not accurate. They are also normally heavier.
This is more a manufacturing process than a type of rifle but does make a different product because of it. They take a barrel blank with a mandril with the rifling inside and then beat it into submission. While it’s getting a good beating it starts to form the barrel around the mandril. This process eliminates the issue of having the rifling cut out since its formed around it. These barrels tend to be more accurate and have higher tensile strengths. When it comes to carbon-based barrels these are superior obviously. It’s easy to have a 1 MOA barrel in this process. This is an expensive process and tends to cost more. They are also heavier barrels. If you’re worried about maximizing barrel life this is what you want. Most people will not shoot enough round through a rifle required to shoot a barrel out though. In my opinion these are over kill for most people.
There are 3 types of stainless-steel barrels that are out there. 410, 416, and 416R. 410 and 416 are two types I’m not going to harp on. They are typically cheap and don’t handle the cold very well at all. So, stay away from them. Now 416R is pure magic. It’s a proprietary blend of magic beans made by Crucible industries. They created a stainless steel that is harder and doesn’t hate the cold, all while being easy to work with. So, what this means for a barrel is they have a long life. They are also much more accurate due to the ease of creating the rifling. You see these in a lot of precision applications. Uncoated you maintain the extreme accuracy but miss out on the extended barrel so add some nitride coating and you have barrel that can rival the life of a CHF barrel with the potential for ½ MOA accuracy if you know how to shoot.
This would really be considered a wrap on the barrel and not really a barrel material. It’s super cool regardless. It’s also super expensive but if repeatable precision is your aim this is your barrel. The barrel is typically a 416R stainless steel barrel milled down to a very thin profile on the outside and then wrapped in carbon fiber. Since carbon fiber is significantly lighter and stronger than all the other materials you get a very light barrel with the accuracy benefit of stainless steel and far greater rigidity than steel. With the increased rigidity of the carbon fiber the barrel also does not see a lot of movement when the barrel gets hot. Carbon fiber is very porous as well, so it lets heat escape faster thus cooling the barrel off quicker. Everything has a give and take though. Science and math all came together, and we have found out you can’t coat the barrel and then apply the carbon fiber. So, you must have an uncoated barrel with carbon fiber. Most people using these are in a precision application or competitive shooter.
Nitride or QPQ
This is a coating that can be done to both steel and stainless-steel barrels that adds a protective coating to the barrel and will increase its life significantly. Well, it’s not really a coating and more of a metal treatment. It creates a protective coating that doesn’t add anything to the barrel. This is important when it comes to accuracy. Your barrel will still be as accurate as it would be uncoated. Just with better barrel life. The only downside to this is it doesn’t handle heat as well as chrome lining. So, you get to keep extreme accuracy but lose some with heat tolerance. What this means is don’t mag dump this in full auto for the few of you that have a full auto rifle. It will handle your semi auto rifle just fine.
This is a coating that you add to the inside of the barrel to give it better heat tolerance and increased barrel life. It can only be done to carbon-based steel barrels. Why? I have no idea. I personally think chrome lining should only be done in rifles that will be fired on full auto regularly. That narrows it down to a very small group of rifles. People seem to buy this because they think it’s better but in a semi auto rifle all it does is decrease your accuracy. Since it must be coated to the inside of the barrel it’s very hard to keep it even enough to not drastically affect accuracy. You won’t find a chrome lined barrel with under 1 MOA accuracy anywhere. It’s very rare to find it much under 2 MOA but It is being done by some master coaters out there.
Well, if you just read that you will know I think a 416R stainless steel barrel (that has been nitrided) is the best for mostly all situations. Except for full auto rifles. In that case get a CHF chrome lined barrel. The Mitchell Defense GWOT Doc comes with a ½ MOA 416R stainless steel barrel that has been nitrided if you’re wondering. If you want the pinnacle of repeatable accuracy, go with a carbon fiber wrapped barrel like the SOIDC Doc has. It’s a repeatable tac driver.