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AR-15 Frequently Asked Questions

Desert Tactical Solutions AR-15 FAQ

 

Q: Does barrel length help with accuracy?

A: Not directly. Barrel length helps with velocity of the bullet. The longer the barrel the more velocity is built up by the expanding gasses behind the bullet. Shorter barrels can be just as accurate as longer barrels but the bullet will have less velocity so at longer ranges the bullet will drop faster. 

 

Q: What are the common barrel lengths?

A: Common AR-15 barrel lengths are 10.5", 12.5", 14.5", 16", 18", 20" and 24". Any barrel with an overall length (OAL) shorter than 16" requires a SBR (Short Barrel Rifle) tax stamp through the BATF. A 14.5" barrel can be made into a 16" OAL barrel if a muzzle brake/compensator/flash hider is pinned and welded to it (permanently attached).

 

Q: What barrel length should I choose?

A: This depends on what the rifle is for. Shorter barrel rifles are obviously much easier to use in close quarters. But a 10.5" barrel isn't going to get the bullet moving fast enough to hit a target at 400 meters very easily once you factor in bullet drop and wind. In general I recommend at least a TRUE 16" barrel (not a 14.5" with an OAL of 16"). A real 16" barrel does not require a tax stamp, which means you don't have to deal with the BATF, you can remove your muzzle device whenever you want and make other modifications without all the hassle a 14.5" with a pinned and welded muzzle device does. A true 16" barrel will end up being about an inch longer than a 14.5" that is pinned and welded. That extra inch isn't significant when it comes to close quarters (neither 14.5" or 16" is ideal for close quarters). But that extra inch can give you an extra 100-150 feet per second of bullet velocity that you won't get from a 14.5 with a 16" OAL because the muzzle device isn't helping with velocity. If you need a gun for true close quarters work (getting in and out of cars, going inside of houses) then go with a 10.5" or 12.5" barrel and get the tax stamp. Otherwise stick with at least a true 16" barrel which is a good all around barrel length. If you like to do longer range shooting an 18" barrel is very good. A 18" barrel will get increased velocity over a 16" and you are at the point of diminishing returns when it comes to barrel length vs velocity.

 

Q: What is barrel twist?

A: The barrel twist ratio is the number of revolutions for the bullet per barrel inches. A barrel that is a 1:9” twist means that the rifling will spin the bullet one revolution in 9 inches. A "slow" twist rate would be a 1:12 barrel and a "fast" twist rate would be 1:7. The rifling twist stabilizes the bullet in flight. In general a slower twist rates stabilize lighter bullets and faster twist rates stabilize heavier bullets. Without getting into the history on bullet twist rates in the AR-15; most barrels today come in 1:12, 1:9, 1:8 and 1:7 twist rates with 1:9 and 1:7 being the most common. The ideal twsit rates and bullets are below:

 

Barrel Twist Ratio
Bullet Weight Range
1:12
30gr-55gr
1:9
45gr-70gr
1:8
50gr-80gr
1:7
55gr-85gr

The above is not a set in stone rule. You could have two 1:9 barrels and one of them will be able to stabilize a 70gr bullet and the other won't. The above is just a general safe range. 

 

Q: What is the best twist rate?

A: This depends on the kind of shooting you do and what bullets you use. The heavier bullets perform better at longer ranges as they are not blown off course as much by wind. Most self defense ammo is also in the heavier weight range of 62gr-77gr. A downside is that it is thought a faster twist rate may wear out the barrel faster. If you do small varmint hunting (squirrels, ect) then a slower twist rate used with smaller weight bullets would be appropriate. For the average person that keeps an AR-15 for some target practice and self defense a 1:9, 1:8, or 1:7 barrel would be fine.

 

Q: What are the different Gas Length systems?

A: There are three types of gas lengths. Carbine Length, Mid Length and Rifle Length. The Carbine Length gas systems are always used on shorter barrels less than 14.5". A 14.5"-16" barrel could have either a Carbine or Mid Length gas system. An 18" barrel or longer should have a Rifle Length gas system. The shorter length gas systems tend to have a bit more recoil and in general are a bit harder on the gun but that would mostly be felt at full auto and not as much under semi auto operation.

 

Q: What is the difference between a Chrome Moly barrel vs Stainless Steel barrel?

A: Chrome Moly barrels in general will last longer than Stainless Steel barrels but Stainless Steel barrels are more accurate. The average person will not shoot enough rounds to wear out even a Stainless Steel barrel. However the accuracy difference really doesn't come into play until you are shooting out past 300 yards. If you are going to be using the rifle to shoot at targets within 300 yards there is no real reason to get a Stainless Steel barrel.

 

Q: What is the difference between chrome lined vs non chrome lined?

A: Chrome Moly barrels can be chrome lined or not. The chrome lined barrels are technically slightly less accurate but the difference is so little most shooters would not be able to tell the difference. The military insists on chrome lined barrels because cleaning a chrome lined barrel is much easier. Chrome lined barrels will also last longer.

 

Q: What is a Cold Hammer Forged (CHF) barrel?

A: Cold Hammer Forging is the process under which a barrel was constructed. It creates a stronger barrel which also costs a bit more over cut or button rifled barrels which are much more common.

 

Q: Do I need to brake in my new barrel?

A: This is a topic of a lot of debate. The general accepted "standard" (if you can call it that) is that a chrome moly or chrome lined barrel does not need a brake in period. Clean it once you get it, then go shoot it. Stainless Steel barrels will sometimes come with a manufacturer suggested "brake in guide". Usually it involves a series of shooting a single round and cleaning the barrel then shooting several rounds and cleaning the barrel in some sort of order. If the barrel comes with a brake in guide its a good idea to follow it. My personal experience is that I have never done any damage to a chrome moly or chrome barrel by not doing a brake in. I have one 18" stainless steel barrel and I did do the brake in that was suggested by the manufacturer and that is a very accurate barrel. Had I not done the brake in I have no idea if the barrel would be any more or less accurate.

 

Q: What is the difference between a .223 chamber, 5.56 chamber and .223 Wylde?

A: The 5.56 round creates higher pressures than the .223 round. Some rifles are only chambered in .223. It is sfe to shoot .223 in a 5.56 chambered rifle but could be dangerous to shoot 5.56 in a .223 chambered rifle. There is also the .223 Wylde chamber which can also shoot both .223 and 5.56. It is typically found on match grade barrels and isn't that common. In general most people should look for a rifle that is chambered in 5.56 so that you can safely shoot 5.56 and .223.

 

Q: What is the difference between piston systems and direct impingement?

A: A piston system does not blow all of the expanding gasses back into the chamber like the direct impingement system does. This makes cleaning the rifle quite a bit easier and means the gun runs cooler. But there is a cost. A piston system will cost at least a few hundred dollars more, and parts are not as common for it. Also a piston system tends to create a bit more recoil which could degrade the accuracy of the shooters follow up shots. A piston system also weighs more in the barrel area.Some people claim a piston is "more reliable" than direct impingement. That is only true if you are lazy when it comes to cleaning your rifle.

 

Q: Are guns parted together from many different manufacturers less reliable than a complete gun that comes from the same manufacturer?

A: The AR-15 platform has fairly high tolerances where all the parts need to be the correct size otherwise they won't work together. The good thing is most AR-15 manufacturers built good parts that all work together without a problem. As long as you stick with good quality manufacturers parts you will not have a problem. I have guns where the lower receiver, lower parts kit, stock system and upper receivers are all made by differentmanufacturers and I never have a problem with them.

 

Q: What kind of AR-15 do you recommend for self defense?

A: For a self defense rifle a 1:7 twist 16" chrome lined barrel with a Mid Length gas system chambered in 5.56.

 

Q: What is the difference between a Mil-Spec Stock/Buffer Tube and a Commercial Stock/Buffer Tube?

A: The Mil-Spec buffer tube has a diameter of 1.148 which is slightly smaller than the Commercial buffer tube which has a diameter of 1.168. The back of the Mil-Spec buffer tube is flat where as a Commercial buffer tube the back of the tube is angled at a 5 degree angle. The Commercial tube is not milled down to the Mil-Spec size and is cheaper to produce. Both tubes will fit on a standard Mil-Spec lower receiver. Any Mil-Spec stock will only work on a Mil-Spec buffer tube and any Commercial stock will only work on a Commercial buffer tube.

 

Q: What is a Flash Hider?

A: Flash Hiders are meant to suppress the flash that may come out of a barrel due to unburnt powder in the barrel. The typical A2 Flash Hider found on most AR-15s does a pretty good job of suppressing flash. The A2 Flash Hider is also a compensator although its primary job is to reduce flash.

 

Q: What is a Compensator?

A: Compensators (AKA "comps") are meant to reduce the amount of vertical barrel rise by forcing some of the gasses upward to keep the barrel down. Some compensators will also reduce some flash but not as well as a true Flash Hider. Compensators can also be a bit louder than a Flash Hider.

 

Q: What is a Muzzle Brake?

A: Muzzle Brakes are meant to reduce the amount of recoil that is felt by the shooter. Most of the gasses are directed out the sides of the Muzzle Brake. This can drastically reduce the recoil but usually results in a large fireball which can kill your night vision at night. Muzzle Brakes are also very loud and due to the shock wave that is sent out the sides can be quite annoying to shooters next to you. Muzzle Brakes can also kick up a lot of dust when shooting from the prone position. For these reasons Muzzle Brakes are generally only used in competition shooting.

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