Posted by Gun Point Custom Shop on June 13, 2016
The AR15 is a the ultimate modifiable weapon - there are multiple configurations that are possible and you can easily get confused about what you need to your intended purpose. The tactical gear you add on to your AR15 can also get into the mix and further complicate what you are looking to do with your firearm.
The first thing you want to do is identify the purpose that your weapon is going to be used for before making any major modifications. This includes choosing a AR15 barrel and all other future weapon additions. All components you add should be factored in with the barrel in mind.
1. Barrel Length
The total barrel length is very important depending on the purpose for which the weapon is going to be used. Key Notes: a short barrel is not designed to engage long range targets and will be a disadvantage for long range shots on the bull’s-eye due to the reduced muzzle velocity. Short barreled AR's are designed for CQB (Close Quarters Battle) where maneuverability and easy target acquisition is most important. The best possible choice if you are going to use it for long range targets is a long barrel, perhaps as long as 20” maximum for a 5.56 NATO or .223 Wylde barrels. Anything longer will drop muzzle velocity because the barrel is too long for the powder burn.
2. Barrel Twist Rate/Rifling
The kind of ammo you plan on using will determine the best barrel twist rate or ratio for your AR15 rifle. the most common barrels usually have 1:7 or 1:9 ratios and these are best for shooting 55 or 62 grain ammunition.
The bullet is also the accompanying consideration for this. The best choice is to get a 5.56 barrel, because it will allow you to shoot both 5.56 and .223 ammo. The reverse is not recommended (don’t shoot 5.56 out of a .223 barrel). The .223 Wylde barrel chamber is also a newer option where you can use both 5.56 NATo and Standard .223 ammunition.
4. Barrel Contours/Profile
The military standard is a M4 contour. the M4 profile offers a marriage of good strength, weight and durability. When weight is an issue a pencil barrel is easy to swing around but it does fall short of performance in the long run and can not stand the heat during extended automatic fire. Heavy barrels are tough and durable, able to withstand even the most heated and rugged firing conditions.
5. Gas System length
You have an option of Carbine, Mid, or Rifle length gas tube. It’s important to understand how the gas system on an AR-15 works. The length of the gas system should increase as the barrel length increases. The reason has to do with “dwell time” – the length of time that the bullet is in the barrel after the shot is fired. On a longer barrel, the dwell time will be longer, because the bullet has to travel a longer distance. Specifically, there is a tiny amount of time when the bullet is traveling through the barrel and it is past the gas port, but it’s still in the barrel. During this time, there is hot gas traveling through the gas tube into the receiver. As soon as the bullet leaves the muzzle, the gas stops flowing. If there is too much barrel length after the gas port, then too much gas flows into the receiver and it can causes issues with excessive recoil and wear on the rifle. If there is not enough barrel length after the gas port, then too little gas flows into the receiver and the rifle may not cycle or may jam.
The AR15 barrel material used must be considered as it can have a tactical advantage or disadvantage for your weapon. Chrome lining can help with corrosion resistance if your rifle will be exposed to moisture.
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