AR-15 FAQ

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1) What is the difference between an A1, A2 and A3 receiver?
A: The A1 and A2 receivers have fixed carry handles with the rear sights built into the handle. The A1 sights require the use of a tool, or the tip of a bullet in the field to adjust them. The A2 sights were upgraded to be finger-adjustable and have increments marked on them. The A3 receiver, commonly called a “flat top” receiver, does not have a carry handle, rather it has a Picatinny rail built into the top of it. This model is designed for easier optics mounting. A detachable carry handle is available for mounting on the receiver.

2) How do I tell what rifling twist rate my barrel has?
A: Many manufacturers will stamp the rifling twist rate on the barrel. They can be found in various locations, though the most common are behind the front sight on top or bottom of the barrel. If the barrel is not marked, the manufacturer may be able to provide this information. As a last resort, you can take the rifle to a competent gunsmith who will be able to determine the twist rate.

3) What is a “large pin Colt” and what will it affect when I’m trying to modify my AR-15?
A: There are two things that are referred to when talking about large pin Colts. The most common is the size of the trigger group pins. Mil-spec pins measure 0.154 inch while many Colt AR-15’s have pins that measure 0.170 inch. Colt has started using 0.154 pins in newer production guns. This is important when the owner of a Colt rifle desires to replace the trigger with a better or match trigger. You must know what size pins your rifle has before purchasing the new trigger. The other part referred to is the front takedown pin on very early models. Often referred to as “green label Colts” these models were produced from 1963 – 1989. The large pin is easily identified by a slotted screw head on both ends and was dropped in 1989 when the “blue label Colts” started to be produced. This would affect replacing the upper receiver assembly with a standard pin size unit.

4) What are the differences between a carbine-length, mid-length and rifle-length handguard?
A: Carbine-length = 6.75 inches
Mid-length = 8.5 inches
Rifle-length = 12 inches
These lengths are approximate and may vary slightly between manufacturers. If your handguard measures 6.5 inches long, it is a carbine length, 8.25 is mid-length, etc.

5) Will standard AR-15 furniture fit my Armalite AR-10?
A: No. The AR-10 is a larger version of the AR-15 and requires different furniture. The DPMS LR-308 does, however, take standard furniture.

6) What are the standard thread dimensions of an AR-15 flash suppressor?
A: The standard thread dimensions are 1/2 x 28. Some custom guns may vary from this.

7) What is the difference between a mil-spec and commercial stock tube?
A: Mil-spec tubes have a slightly smaller diameter. A commercial tube will have an outside diameter of 1.168 inches while the mil-spec tube will have an outside diameter of 1.148 inches. The difference of 20 thousandths of an inch isn’t very much but a commercial stock may seem loose on a mil-spec tube and a mil-spec stock can be very tight on a commercial tube.

8 ) How can I mount a scope to the carry handle on my AR-15?
A: Several companies make scope mounts specifically designed for carry handle mounting. These attach through a hole in the middle of the carry handle and provide a Picatinny rail to mount optics to. Most of these mounts allow the shooter to still use the iron sights of the rifle when they are installed.

9) How do I tell if my AR-15 is chambered 5.56 NATO or .223 Remington?
A: Manufacturers will often stamp the barrel with the caliber designation. They can be found in various locations, though the most common are behind the front sight on top or bottom of the barrel. If the barrel is not marked, the manufacturer may be able to provide this information. As a last resort, you can take the rifle to a competent gunsmith who will be able to determine the chamber by pouring a cast of it and taking key measurements.

10) I own an Optics Ready model AR-15. What does that mean?
A: Many A3 flat top models come with gas blocks that have a Picatinny rail on the top of it instead of a fixed front sight. In most cases, this front gas block rail is lower than the rail on top of the receiver. When backup iron sights are installed, the front sight must be higher than the rear to offset this height difference. Optics Ready models use full-length rails or gas-block rails that are the same height or on the same plane of the receiver. This system requires the use of backup sights that are the same height.

11) I mounted a scope to my flat top AR-15 and it is too low. What can I do to correct this?
A: Many companies manufacture a part called a flat top riser to correct this problem. This is simply a Picatinny rail that attaches to the top of the receiver and provides an extra ½ to ¾ of an inch of height. For most shooters this is enough to bring the scope up to a comfortable level.

12) I want to mount a flashlight and forward grip to my handguard. What are my options?
A: There are several options for mounting accessories to the handguard of an AR-15. The easiest and probably the least expensive is to attach a single rail to the bottom half of the handguard. Depending on how many accessories you want to attach, you may need to go with a replacement handguard. There are many models available that will provide anywhere from two to four rails. While all will accomplish the same task, weight and cost are probably the biggest factors when choosing a new handguard. A couple of manufacturers also make units that attach to the outside of the standard handguard and provide multiple rails.

13) The trigger pull on my AR-15 is heavy. How can I lighten it?
A: If you are looking for a way to do it yourself, there are two main options. The first is to replace the trigger group springs with lighter ones like JP Enterprises makes. If you can remove and install the trigger assembly, this is an easy job. There are also drop-in replacement triggers available form several manufacturers. Timney and Chip McCormick both make excellent units that are easy to install and are a huge improvement over the stock trigger. The best and most expensive method is to have a gunsmith install a match trigger such as a Jewell. Avoid filing or stoning on the engagement surfaces of the hammer and sear. These parts are surface hardened and if too much material is removed, they will be ruined and can cause major malfunctions.

14) Are all AR-15 magazines interchangeable? Will they fit all models of AR-15’s?
A: In 99 percent of cases, yes. Obviously, due to manufacturing tolerances of the different magazines and firearms, some may not function as well as others. There was also one Orlite magazine made in Israel that would not lock into the Bushmaster guns. There was a ridge on the magazine that interfered with the slightly deeper magazine well of the Bushmaster.

15) I’ve heard of gas piston AR-15’s. What are they and what are the advantages?
A: The original AR-15 uses a direct-gas impingement system. Gases from the fired round travel through a port in the barrel, down a tube that runs along the top of the barrel and into the bolt carrier assembly, thus operating the action. The biggest problem with this system is that it is dirty. Fouling from the fired round is blown directly into the action. If the rifle isn’t cleaned regularly, this fouling can cause malfunctions. The gas-piston system replaces the gas tube with a piston that is actuated by the gases escaping through the port in the barrel. The piston moves rearward, pushing on the bolt carrier and operating the action. Fouling is no longer blown into the action, making this system cleaner and more reliable over a longer period of time. Cleaning isn’t required as often to prevent malfunctions. Entire guns and complete upper assemblies can be bought with the gas-piston system. There are also kits available to convert standard AR-15’s to the piston system.

16) I’d like to shoot .22LR ammo in my AR-15 to save money. What are my options?
A: There are two ways to convert your AR-15 to shoot .22LR ammunition. The first is the conversion kit. This kit replaces the bolt carrier assembly of the rifle with a self contained unit that consists of a .22LR chamber and bolt assembly. These units are generally reliable and inexpensive. The main drawback of the unit is that the barrel is designed to shoot the longer .223 caliber jacketed bullet and may not be as accurate with the shorter, lead rimfire bullet. The other way is to replace the entire upper receiver assembly with a dedicated .22LR assembly. This assembly will shoot only .22 LR ammunition and will have a barrel that is designed for that caliber. These upper assemblies will typically be more accurate than the conversion units. The drawback is that they also cost hundreds more than the conversion unit.

17) I have a fixed buttstock on my AR-15 and would like to install a collapsible buttstock. What parts do I need?
A: All of the buttstock parts will need to be replaced including the extension tube, bolt buffer, recoil spring and stock. It is generally easier and less expensive to purchase a complete buttstock assembly that will include all of these parts.

18) I am reloading for my AR-15 and am tired of picking up brass. Is there a product that catches the ejected brass?
A: Yes. There are brass catchers available from several manufacturers. One style uses a Velcro strap that wraps around the handguard. This unit also has a zippered bottom for easy emptying of the spent brass.

19) My fingers get tired from loading my AR-15 magazines. Are there loaders available to help with this?
A: There are several styles of magazine loaders available. Some load loose rounds while others use rounds on stripper clips. One style, the Lula, can also be used to unload a magazine.

20) Can I safely fire blanks in my AR-15 and if so, what do I need?
A: You can fire blanks in your AR-15. The action will not cycle properly without an adapter though. The adapter attaches to the muzzle of the barrel and creates the back pressure that is normally created by the presence of the bullet. You must clean you rifle thoroughly after firing blanks. They are dirtier than loaded rounds and often times are corrosive.

21) I noticed some play between the upper and lower receivers of my AR-15. Is there a way to tighten this up?
A: There is a nifty little item called the Accu Wedge that is designed to reduce the play between the upper and lower receivers. It costs very little and installs in seconds.

22) I’m a left handed shooter and I have difficulty using the safety on my AR-15. Does someone make a left-hand safety?
A: At least one company makes a safety that is reversible. The most common solution for left-handed shooters is to install an ambidextrous safety. This allows the safety to be operated from the left or right side. Installation isn’t difficult, but does require some disassembly of the rifle.

23) I want to install a collapsible buttstock and replace the barrel on my AR-15. Are there any special tools that I will need?
A: Yes. There is a special wrench for both the collapsible stock nut and the barrel nut. These can be purchased separately but the most economical way is to buy a combination tool. This will have both wrenches on it plus a screwdriver end for the A2 stock bolt and a wrench for removal and installation of the flash suppressor. You will also need a way to secure the upper and lower receivers. A set of vise blocks will hold these in a vise and prevent damage to them while the work is being performed. A handguard tool will make removal and installation of the handguards easier also.

24) Why are there so many different color followers in AR-15 magazines? Are any better than the others?
A: The original AR-15 magazines came with black followers. It was found that these followers could tilt in the magazine during use and cause feed malfunctions. An upgraded follower was introduced to correct this problem and was colored green for easy identification. Since then, there have been other colors introduced like gray and orange. These are supposedly upgrades or different generations of certain companies’ followers. Some even claim to be self lubricating. Avoid using black followers and tilting shouldn’t be a problem.

25) What calibers can I convert my 5.56/.223 AR-15 into?
A: Basically the 5.56/.223 lower receiver can be converted into any caliber that will fit in its magazine well. The most common you will find are .22 LR, 9mm Luger, 6.8 SPC, .204 Ruger, 6.5 Grendel, 7.62x39mm and 5.45x39mm. At least one company offers a .50 BMG upper. This is a single-shot, bolt-action conversion unit.

26) Can I fire 5.56 NATO ammo in my .223 Remington chambered AR-15 or vice versa?
A: While the 5.56 NATO and .223 Remington rounds are very similar, they are not the same. The 5.56 chamber has a longer throat to allow seating longer bullets and the round is loaded to higher pressures. Combine these factors with a .223 chamber with a shorter throat and it could lead to problems such as blown or punctured primers. Damage to the gun and injury to the shooter could also result. Therefore, it is not recommended to shoot 5.56 NATO ammunition in a .223 Remington chambered firearm. You can, however, safely shoot .223 Remington ammunition in a firearm chambered in 5.56 NATO.

27) Can I use the .22LR conversion kit in my AR-10 .308?
A: No. The conversion kit will only work in an AR-15 chambered in 5.56 or .223.