The energy needed to produce threat-stopping wounds is very different and much higher. The short version of the research is that a lighter, faster bullet could be just as effective as a larger bullet up to realistic combat ranges. One of the big debates of the late s and early s small arms engineering community stemmed why the Army insisted on yard capable rifles when most combat happened at far shorter ranges.
Part of the appeal of the AR was that it was a much lighter weapon system than its competitors. Not just the rifle but the corresponding ammunition and support gear as well. Combined, the soldier could carry much more ammunition and participate in firefights for a longer period of time.
This chart shows a plot of starting muzzle velocities of an M projectile fired from various barrel lengths. The red line represents the minimum velocity for M to have good terminal effect. By starting at a higher velocity, you give yourself more time and distance to have maximum effect. Mission drives the gear, so how much range do you need? This is all assuming that you are trying to kill something or stop a threat.
Each one has its pros and cons. What you choose ultimately stems from your goals and needs. I once had a conversation a special operations member who also happened to be a gun nut. He later started up a very successful company that produced well known ARs, barrels, and accessories. The 5. Everything was optimized for it. Clearing a house or riding in a vehicle is more difficult. There are configurations like the M16A5 which help with the maneuverability aspect, but a shorter rifle is always easier in cramped quarters.
I suspect that we would see a lot more The M4 was adopted in after ten years of design and testing. It had a great reputation for compactness and ease of carrying, but the shortcomings of its low velocity and very loud noise signature were a problem.
In fact, it will cause you more pain than it is probably worth due to dealing with NFA paperwork, taxes, and regulation. Some people circumvent this by using This does bring the length back up to the legal Give yourself room to experiment without tripping over federal law. If you want to see a bunch of forum fanboys go at it with one another, ask them the best length for an SBR.
The thread will go on for pages and pages while they hash out the tiny differences between The truth is that these lengths all do the same thing and they do it well.
They all make for very compact and easy handling carbines. They also come with increased pressures, loud noise, and reduced velocity. Keep in mind that this class of AR is purpose-built for close-quarters fighting. After the Gulf War, Armalite floated an idea for a light sniper rifle called Special Purpose Rifle, and it went nowhere.
The concept finally rose to prominence when the GWOT started ramping up in the early s. The Navy signed on and dubbed it the Mk12 program. Eventually, the Army won. But as it tends to go, bureaucratic red tape caused more headaches. They got their barrel. It offers a very smooth recoil impulse due to its full-length rifle gas system while shaving a few ounces off of the end of the rifle.
The length also maintains good velocity for reaching out with a flatter trajectory. The primary trade-off is a loss in dwell time between the gas port and the muzzle. This can make it a little touchy about ammo selection in cold weather. Those who carry rifles professionally do an awful lot more living with their weapons than shooting them.
Mission drives the gear. How are you going use your rifle? Also, as a bonus, we civilians can take advantage of configurations the military never fully adopted. That reduces some of the pain associated with full sized rifles and still provides all the benefits.
This is actually my favorite configuration. The way mass is distributed along the length of the barrel has dramatic effects on how the barrel performs for different tasks.
They both place the round where you aim them. The differences show up at the barrel heats up. You can carry it all day, or you can shoot it all day, but not both. You might remember from your chemistry classes way back in the day that metal expands as it heats up. For rifle barrels, this expansion negatively affects the accuracy of a barrel. So the faster it heats up, the quicker this decrease in accuracy happens.
This was the case at the infamous Battle of Wanat. Most of us will never shoot that much. Skinny barrels heat up faster, so you expect their accuracy to drop off faster.
But they also cool down quicker. Heavy barrels are slower to heat, so they retain their accuracy longer, but also slower to cool down. This produces a well-balanced rifle that dissipates heat well. This has a skinny profile near the receiver and a thicker profile towards the muzzle.
There is kind of a funny story behind how that profile came about. The compromise between weight and balance comes down to how easy you want the rifle to carry, how quickly you want to bring it to a target, how well it settles in your hands for precision shooting, and how well handles heat. You can read more about that in my article on weight and balance. Light barrels are best suited to guns that are carried a lot and see easy to moderate shooting schedule.
This is most people, including military members who live with their rifles. Heavy barrels are suited to rifles that need to maintain higher levels of accuracy over long strings of shots. This describes match shooters and precision rifles shot from relatively fixed positions. Most people are far better served by lighter profiles. Those descriptions are very broad, with many sub-varieties falling under those labels.
Some alloys are more useful than others. The two different alloys have different wear characteristics. This is generalized and ignores the quality of the barrel, rate of fire, heat, or load pressure of the ammunition.
All of these things dramatically affect the life of a rifle barrel. This is the most common type of steel encountered in AR barrels.
If you read my guide to buying your first AR , I mentioned two of them: and In real terms, is a harder alloy and better stands up to temperature extremes, such as fully automatic fire or very cold weather.
While the higher carbon content of steel does make it stronger at the edges of performance, the average person will probably never push their barrel to that limit.
This is why some manufacturers use steel as a cost saving measure. This specification is MIL-BE , and lists out the chemical composition required to be compliant.
Of note, the third blend in this spec includes Vanadium. You may also see it called 41V45 steel. The vanadium in this alloy helps promote a finer grain structure, wear resistance, and strength. Being both and E certified is more difficult, and thus more expensive. Stainless barrels are popular for match rifles for one primary reason: they are easier to machine and finish. The same small shop is able to machine, rifle, polish, and lap all in one place.
Working with stainless steel also reduces the wear and tear on tooling. Due to a shortened supply chain and skilled craftsmen all working in one place, the finished product is cleaner and more consistent from barrel to barrel. Speaking of finishes inside the bore, another factor is protective linings.
Historically, the application of chrome lining to rifle barrels meant that the bore surface became uneven and inconsistent. These inconsistencies disturbed the bullet and reduced accuracy.
Of course, this varies from manufacturer to manufacturer. The trade-off is that stainless barrels do not handle adverse conditions as well. Due to the necessary inclusion of sulfur in the metal, there is a risk of developing sulfide stringers. The best way to prevent that is to increase the barrel thickness and avoid very cold or very hot temperatures. The trade-off is that without the extra sulfur, the barrel becomes brittle in temperatures below freezing.
To compensate for temper embrittlement, the walls of the barrel must be thicker. If you see a barrel advertised as stainless, ask if it is actually r before you buy it. The temper embrittlement issue in steels with extra sulfer isn't unique to stainless barrels. The same applies to steels. The key factor in overcoming this issue is how the barrel was tempered by the manufacturer. This is where the real differences between chrome moly CM and stainless barrels become apparent.
CM and stainless barrels, machined bare, have about the same level of accuracy. CM barrels require extra lining, typically composed of chrome, to resist corrosion. In the 21st century, manufacturers like Criterion have figured out how to get a more even and consistent layer of chrome in the bore. The bottom line is that chrome lining does not deserve the negative accuracy reputation it has today- so long as it comes from a quality manufacturer.
Another popular option is nitriding. Nitriding is a surface conversion process whereby manufacturers submerge the barrel in a nitrogen-sodium solution and heat to a high temperature, u sually between and degrees. Remember this temperature for later. This case is about Rockwell, as opposed to found on normal barrel steel. Nothing is free , though. There are two downsides that I know of. The first is the temperature required to complete the process, which is very close to those used for stress relieving barrels after rifling.
More on that in a second. Secondly, the nitride case is much less heat resistant than chrome. It is not an ideal solution for barrels that see very high volumes of sustained rapid fire. Well-made barrels are more than capable of turning in 1 to 1. If you absolutely need better than 1 MOA accuracy, and you only plan to feed it quality match ammunition, then go ahead and get a stainless barrel.
If you live where it gets below freezing, stick to r stainless. Like a spiraling football, this spinning action increases the accuracy and range of the projectile. We measure how stable a bullet is by applying a gyroscopic stability factor. The stability factor is a combination of the spin rate and the shape of the bullet. There are three methods that manufacturers use to form the rifling of a barrel: cutting, button rifling, and hammer forging.
Each of these has pros and cons and the balance is between how long it takes, the consistency of the end result, and how much stress the steel undergoes during the process. A machine cuts each groove one at a time over many passes. This produces the least amount of stress on a barrel but requires the most care to get right. Generally, these are the most expensive barrels due to the extra time and quality controls required.
This is a much faster method but produces much more stress on the barrel steel. Germany developed this method during WWII as a way to accelerate machine gun barrel production.
There is a great article from a edition of Precision Shooting that covers the history and process well. This is a fast way to mass produce very consistent rifle barrels. It has a side benefit of creating a metal grain compression pattern and a slightly stronger barrel. The downside, of course, is that it puts a very high amount of stress on the barrel steel.
There are only a handful of companies with hammer forging machines in the US. If you are buying a hammer-forged barrel, it probably came from one of these plants. This video demonstrates what the process looks like. It is from GFM Machine, which produces most of the hammer forging machines in the world. One of the original engineers who designed the process founded the company. Applying high amounts of force on steel results in stress.
Once you have the go-ahead, you may add a foregrip to your pistol. A pistol is not. If you genuinely want to trick out your rifle with numerous tactical attachments , including foregrips, scopes, and muzzle devices, then opt for a full-length rifle.
Then you can choose which parts to attach, which accessories to mount, and what caliber you fire. What Size Barrel Length is Legal? Do you want to stay ATF compliant? 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. Check out our other handguards as well! All of these handguards will keep your AR accurate, safe, and lightweight. Your email address will not be published. Of course, since the various components of the upper can […]. Any use of this content without express written consent is prohibited.
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