AR Barrel Length How to Pick

These are standard barrel lengths and though others exist in between this list should suffice as to giving you a very good idea  of how to choose.

A) 10 inch barrel (or less) AR Pistol. To have an AR qualify for the shortest barrel there must be no but stock attachment. The gun is considered a pistol as it can be fired with one hand. Rifle powder does not burn up all at once but burns the whole length of the barrel as it pushes the bullet. By shortening the barrel muzzle flash is extreme. Though similar to the Israeli UZI for daytime use if there was ever a war the gun fired at night would draw fire from anyone seeing the flash. The moment you put a stock on this gun it is considered an illegal gun. The UZI uses a 9 MM pistol case pistol powder burns immediately because the gun has a short barrel it needs the push all at one time and thus lessons muzzle flash. The 10 inch AR barrel lessons bullet rang and so this gun should be considered a short range gun. Some have noted that the short gas system can lead to short stroke which means the shell you just fired does not eject. In looking back at the gas system explanation the barrel length after the gas port determines pressure to extract the last round. With such a short barrel the gas system inefficiency could cost you your life with a short stroke at the worst possible time. Deficiencies in the past
1) muzzle flash
2) short range
3) possibility of jamming. Some have said that using the heavier 77 grain bullet helped with function. And others have mentioned some function problems have been overcome. This is not a gun I would own!

B) 14.5 inch barrel AR rifle M4 military configuration This is only legal for a civilian to own if the person takes the barrel to a gun shop and permanently has the muzzle break welded to the barrel bringing its overall length out to slightly over 16 inches. If doing an AR Build take the bolt and barrel to the gun shop and have him check the head space first as with current higher AR production rates some barrels are not head spaced right and making it past quality control and if he welds the muzzle brake on the gun barrel you will not be able to exchange it. This is a fine close quarter’s barrel and you can still have about mid range capabilities and use a collapsible stock. (It is too much trouble is to keep it at 14 inches and pay for a $200 tax stamp and go through a enhanced FBI background check which checks mental stability etc. )
  

C) 16 inch barrel AR rifle M4 civilian configuration.  The advantages of picking this barrel over the one above will be obvious. This barrel has some unique abilities and that is it is still an excellent close quarters gun and has the ability to use a collapsible stock shortening the guns overall length. If you use a thread protector instead of a muzzle brake then the barrel will be the shortest possible legal length adding grater muzzle velocity and grater range. Plus factors over the 14.5 barrel which must have a muzzle brake welded on. The gun is 16 inch
1) The overall gun length is the same as the gun with a 14.5 inch barrel.
2) slightly longer accurate range
3) Overall gun barrel is the same length using a thread protector and the muzzle brake can be legally screwed on and taken off of the gun and can be switched unlike the 14.5 inch barrel.

D) 18 inch barrel-  Not one of the more popular AR barrels two inches shorter than the 20 inch barrel and though offering grater range; when a muzzle brake is screwed on the gun barrel it will be about 20 inches. so why not own a 20 inch barrel and take advantage of the longer range and muzzle velocity. The gun is beginning to sacrifice some of its close quarter’s ability.

E) 20 inch barrel AR rifle Originally the M16 this AR offers longer range than the 16 inch barrel M4 and even today the 20 inch barrel has US military usage and is excellent for open field fighting. For civilian use it is excellent for target, and varmint hunting. On the overall the AR line of guns are considered mid-range guns. Militarise around the world have generally moved towards mid-range weapons. The ammo is smaller and you can carry a lot more of it. The guns are lighter and more manageable fits in well quick attacks and fast troop movements needed situations.

Barrel Heavy and Contoured

 F) HBAR Heavy barrels are generally for target shooting and would be impractical for all day rapid movement where the gun must be carried for long all day walking hunting.

      

Contoured Barrels

Made to be as light as possible and would be more practical for long walking hunts.
Richard W. Norman author of American Handbook on Guns Ammo and Freedom