It doesn't exist. If you want to shut down any other arguments about barrel steel and mil-spec certifications yourself, download the full version of MIL-BE here. Then, happily share it and spread some truth. Every barrel needs to be treated and coated with some sort of protective finish. Nearly all AR barrels sport a matte black finish and some sort of treatment for the rifling inside.
Even some stainless barrels have their rifling and exterior treated with an extra layer of protection. But there are many ways to achieve this look and protection. Let's break 'em all down:. You've probably seen these two phrases quite a lot, but they're one in the same. Melonite is just a branded name for the process of nitride-treating a barrel. This finish is achieved by submerging the barrel in a "ferritic nitrocarburizing" salt bath.
Basically, the barrel's heated to around 1, degrees and submerged in a liquid mixture of nitrogen, oxygen, and carbon. These elements are thus forced into the steel. These three elements bind and create a layer that bonds with the steel itself.
If you're not familiar, that is an incredibly hard rating. This gives the barrel superior life and accuracy. As a freshly nitride-treated barrel is first exposed to oxygen, it turns a dark, matte black color.
A manganese phosphate finish sometimes called a Parkerized finish, which is a brand name coats the barrel with a matte black texture, similar to a nitride treatment. The manganese element creates a dense, slight porous, crystalline structure atop the steel. This coating allows the metal to absorb oil and lubrication, and it seals the raw steel underneath from the elements.
A manganese phosphate finish also sports a high Rockwell Hardness rating, though it isn't as hard or protective as a nitride finish. Phosphate finishes are less expensive than nitride treatments and the process of applying them is easier. Most phosphate finishes are applied at around degrees - a stark contrast to the conditions required for a nitride finish. Chrome lining is a treatment applied to the inside of an AR barrel. During this process, chrome is applied to the lands and grooves of the barrel's rifling, as well as the chamber.
In order to ensure accuracy with this extra material, chrome-lined barrels are typically bored out more than the final internal diameter. The tolerances are made up by adding the chrome to the inside of the bore.
Chrome lining was popular for many years. Advancements in nitride treatments have largely made chrome lining obsolete. Less expensive barrels are sometimes chrome-lined to make up for their lower hardness rating. Whew, that was a lot of info to digest. We know there are endless factors to consider when buying your black rifle's barrel, but here's a quick recap of the big points and best practices:.
Got more questions about AR barrels, how to build one, or something else related? Get in touch with us. We're happy to talk over the phone or through email. We've all built our own guns in our spare time and we're glad to be a source of information. Best Sellers. How twist rate affects accuracy When we throw a football, we impart spin on it to stabilize it and to help it go where we aim.
There ain't no "one size fits all" Unfortunately, there is no "universal" twist rate that works for every single cartridge on the market. The twist rate Goldilocks When a round isn't stabilized, it usually tumbles end-over-end and hits its target in what is commonly called a "keyhole" shot. Picking the right twist rate Many shooters, even professionals, will casually tell you that picking the perfect twist rate hinges on the weight, or grain count, of the bullets you're shooting.
It's not about the weight While Bob might be right, his reasoning isn't completely correct. The Golden Rule of twist rate Ready for it? Optimal twist rate for Blackout Blackout was designed to be fired in a subsonic, suppressed configuration while affording the ability to shoot as supersonic rounds, too.
Best twist rate for. How barrel length affects accuracy Technically, barrel length doesn't affect accuracy at all. It's all about speed The only purpose a barrel's length serves is to get your round up to its optimal velocity, so the rifling inside the barrel can spin it appropriately and get it moving in a relatively flat trajectory. Length, velocity, and diminishing returns Picking the right barrel length comes down to figuring out diminishing returns.
Finding a balance Basically, you need to figure out the point at which adding more barrel yields little to no extra velocity. But suddenly, we get to 16" and some weird stuff happens: Remember Goldilocks? Nonetheless, let's quickly look at these three rifling and manufacturing processes for the sake of knowledge: Cold-hammer forged barrel Cold-hammer forged CHF barrels are among the most popular types of barrels found on the AR market today. Cut-rifled barrel Cut rifling is an old-school method of making a barrel.
Button-rifled barrel Button-rifled barrels are manufactured under extreme pressure like CHF barrels, but in a different way.
Which barrel rifling method is best? Chromoly Vanadium This is the gold standard steel of AR barrels. That document details exactly what materials need to be present in a rifle barrel for it to be considered mil-spec: Would you look at that? Types of Barrel Treatments Every barrel needs to be treated and coated with some sort of protective finish. Manganese Phosphate "Parkerized" A manganese phosphate finish sometimes called a Parkerized finish, which is a brand name coats the barrel with a matte black texture, similar to a nitride treatment.
Chrome Lining Chrome lining is a treatment applied to the inside of an AR barrel. Conclusion Whew, that was a lot of info to digest. We know there are endless factors to consider when buying your black rifle's barrel, but here's a quick recap of the big points and best practices: There is no "universal" twist rate for the standard AR Most ARs chambered in 5. Barrel length doesn't equal accuracy, velocity and twist rate does.
Only buy a barrel that's long enough to maximize velocity before diminishing returns. Most barrels' rifling is formed by cold-hammer forging or by button rifling. Nitride and phosphate coatings are the most common barrel finishes. Chrome lining can also be applied to rifling to increase barrel life. At lower. We encourage each and every builder to perform their own research around their respective State laws as well as educating themselves on the Federal laws.
But what does more velocity mean? Although, a longer barrel means a greater trajectory of the round and that means that there is going to be greater energy forced into your target. It also allows you to extend the range on your AR. For those of you who are new shooters, the longer the barrel, the more of an effect barrel whip will have. For long-range targets, the longer the barrel the better.
This is really the only case when velocity equals accuracy. Another important aspect of your perfect barrel is the type of gas system that you use.
Again, for those new to shooting, your gas system in your AR is an integral part of your upper assembly. Simply, the point of your gas system is that when you pull the trigger of your AR, a bullet will come out and that bullet is pushed by an explosion caused by gun powder. The powder makes a gas that is pushed through a gas tube. This gas essentially pushes out the bullet case, making the need for a bolt-action unnecessary.
This allows for semi-automatic fire. If you like a longer barrel, then shoot with a longer barrel. If you like a shorter barrel, shoot a shorter barrel. Whatever you choose, Bootleg has a quality selection of handguards to cover your barrel and for you to add all sorts of other accessories on there.
If you will be shooting at longer distances, a longer barrel offers increased accuracy and sufficient pressure to enable peak ammo acceleration. A shorter, lighter barrel is a better choice for maneuvering in confined areas or protecting your home.
Also, keep in mind that adding one inch of length to a shorter barrel can result in a foot-per-second velocity increase of up to feet.
Most AR owners can get by with a standard mil-spec barrel. However, heavy users will experience greater long-term benefits from a cold-hammer-forged barrel, which entails a process that uses a large hydraulic machine to hammer the barrel blanks from multiple sides. This produces a slightly tougher, more durable barrel with a longer lifespan than its mil-spec counterpart. The profile refers to the weight of the barrel. Profiles are broken down into three basic categories: lightweight, government, and heavy.
The heavier the barrel, the greater the resistance it provides to the buildup of heat when firing the weapon. A heavier barrel will last longer than a lighter one, making it a better choice for frequent AR users. On the other hand, a lighter barrel makes the gun easier to carry. The M4 government version is the most popular profile option, as it offers an acceptable compromise for many AR owners between heavier and lighter barrels. Mil-spec AR barrels typically include a lining made of chrome poly steel for reasons that pertain mainly to longevity and cleanliness.
The chrome lining is beneficial for military use in high-humidity and saltwater environments because it offers excellent resistance to corrosion.
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