For a long time, everyone and their brother wanted a chrome-lined barrel. They’ll pay extra for it. They’ve heard it’ll last almost forever. They’ve heard it’s the best barrel that ever existed.

And they’re only partly correct.

Chrome lining can protect the barrel from heat and pressure. That’s true.

A good chrome lined barrel can still last for 5,000 rounds before you see any degradation. Maybe more.

However, chrome lining can be uneven in barrels, depending on the manufacturer. The barrels can be SLIGHTLY less accurate than a non-lined barrel (you ARE lining the rifling inside the barrel and therefore there is a slight coating over the lands and grooves, dulling them ever-so-slightly.)

Essentially, chrome-lining is one of those leftover processes that “a guy at the range heard from his buddy at work that his dad always told him…” that chrome-lining was the ONLY kind of barrel you’ll want/need.

This is not to take away from chrome-lined barrels. Like I said, they protect against heat and pressure in an AR. It’s not to say that there are zero benefits to using one.

But there are a LOT of other choices when it comes to barrel treatments. See also Meloniting, Gas Bed Carborization, and Cryogenic Tempering

The bolt holds the round in place ready for you to pull the trigger, which releases the hammer. The hammer strikes the back of the firing pin pushing it through the bolt to strike the primer on the round thereby firing it. The bolt is subjected to the highest amount of stress in your AR.

For that reason, don’t go cheap when choosing your bolt. Rather than go with Carpenter 158 steel for your bolt, FSD recommends 9310 steel. The Carpenter steel is just too brittle. Sure, the 158 is cheaper, but it WILL break – and when it does, your gun is down until you find a new one.

A detent is a generic term used to mean a device, mechanism (in this case, a pin) which essentially keeps another part from moving, forces it to move in one direction, or holds one part in place.

The AR-15 has several detent pins (and detent springs) to allow the firearm to function properly. For example, in the lower parts kit, you’ll find:

A detent is a generic term used to mean a device, mechanism (in this case, a spring) which essentially keeps another part from moving, forces it to move in one direction, or holds one part in place.

The AR-15 has a couple of detent springs to allow the firearm to function properly. For example, in the lower parts kit, you’ll find:

  • Pivot Detent Spring
  • Takedown Detent Spring

From Wikipedia:

Eugene Morrison Stoner (November 22, 1922 — April 24, 1997) was member of the US Marine Corps in WWII and a firearms designer who is most associated with the development of the AR-15 rifle that was adopted by the US military as the M16. He is regarded by some historians as one of the most successful firearms designers of the 20th century, along with John Browning and Mikhail Kalashnikov.

eugene stonerIn late 1945 Stoner began working in the machine shop for Whittaker, an aircraft equipment company, and ultimately became a Design Engineer. In 1954 he came to work as chief engineer for ArmaLite, a division of Fairchild Engine & Airplane Corporation. While at ArmaLite, he designed a series of prototype small arms, including the AR-3, AR-9, AR-11, AR-12, none of which saw significant production. Their only real success during this period was the AR-5 survival rifle, which was adopted by the United States Air Force.

In 1955, Stoner completed initial design work on the revolutionary AR-10, a lightweight (7.25 lbs.) selective-fire infantry rifle in 7.62 x 51 mm NATO caliber. The AR-10 was submitted for rifle evaluation trials to the US Army’s Aberdeen Proving Ground late in 1956. In comparison with competing rifle designs previously submitted for evaluation, the AR-10 was smaller, easier to fire in automatic, and much lighter. However it arrived very late in the testing cycle, and the army rejected the AR-10 in favor of the more conventional T44, which would become the M14. The AR-10’s design was later licensed to the Dutch firm of Artillerie Inrichtingen, who produced the AR-10 until 1960 for sale to various foreign military forces.

At the request of the U.S. military, Stoner’s chief assistant, Robert Fremont and Jim Sullivan designed the AR-15 from the basic AR-10 model, scaling it down to fire the small-caliber .223 Remington cartridge, slightly enlarged to meet the minimum Army penetration requirements. The AR-15 was later adopted by United States military forces as the M16 rifle.


After ArmaLite sold the rights to the AR-15 to Colt, Stoner turned his attention to the AR-16 design. This was another advanced 7.62 mm rifle but used a more conventional piston and a number of stamped parts to reduce cost. This weapon saw only prototype development but adaptation to .223 resulted in the somewhat successful and often imitated Armalite AR-18.

Stoner left ArmaLite in 1961 to serve as a consultant for Colt. He eventually accepted a position with Cadillac Gage where he designed the Stoner 63 Weapons System. This was a modular weapons system that could be reconfigured to be a standard automatic rifle, a light machine gun, a medium machine gun, or a solenoid-fired fixed machine gun. The Stoner Weapons System used a piston-operated gas impingement system, though Stoner himself believed direct gas operation was the ideal method for firearms. Once again, Robert Fremont and Jim Sullivan would take a Stoner rifle and redesign it for the .223 Remington cartridge, to create the Stoner 63 Weapons System.

Stoner worked for TRW by designing the TRW 6425 25 mm Bushmaster auto cannon, which was later manufactured by Oerlikon as the KBA.

He co-founded ARES Incorporated of Port Clinton, Ohio, in 1972, but left the company in 1989, after designing the Ares Light Machine Gun, sometimes known as the Stoner 86. It was an evolved version of the Stoner 63. At Ares, he also designed the Future Assault Rifle Concept (FARC).

In 1990, he joined Knight’s Armament Company (KAC) to create the Stoner Rifle-25 (SR-25), which currently sees military service as the United States Navy Mark 11 Mod 0 Sniper Weapon System. While at KAC, he also worked on yet another version of the Stoner Weapons System, called the Stoner 96. Among his last designs were the SR-50 rifle and the Colt 2000.

A firing pin is a movable pin in a firearm that strikes the primer of a cartridge to set off the charge. In the case of the AR-15, it is located in the bolt carrier group and can be easily exchanged in the event that it is damaged or ceases to function properly.

In the AR-15 bolt carrier group pictured here, the firing pin is the silver-colored item in the middle of the picture.

In the AR-15 bolt carrier group pictured here, the firing pin is the silver-colored item in the middle of the picture.

Also called “Flash Suppressor”, “Flash Guard”, “Flash Cone”, or “Flash Eliminator”.black-rain-ordnance-ar15-flash-hider

A flash hider is a device which attaches to the muzzle of a rifle that helps to reduce the amount of flash/light seen by the shooter while firing by cooling or dispersing the burning gases that exit the muzzle.

The main purpose of a flash hider is to lessen the flash that the shooter sees when the firearm is discharged. A common misconception is that it’s primary goal is to lessen the flash signature seen by the enemy when the gun is fired. Fhider_SG_KFH_BK_lg

Flash suppressors are very different from muzzle brakes! While they are both located/mounted in the same place on the AR, muzzle brake is used to reduce the perceived recoil a shooter experiences (and typically has zero to do with eliminating flash), while the flash suppressor only limits the amount of flash the shooter sees and usually does not affect recoil.


Fixed A2 Front Sight Post with Integrated Gas Block

Fixed A2 Front Sight Post with Integrated Gas Block

Gas blocks serve an important role in the function of your AR-15.

Whether rail height, low profile, or part of a fixed A2 front sight post, the gas block holds the gas tube in place, which is key to the cycling of your AR.

Gas blocks are precisely positioned over the gas port in the barrel of the AR. When a round is fired, the bullet travels down the barrel, propelled by gas. Once the bullet passes the gas port in the barrel (a tiny hole in one side of the barrel), the gas is forced through the gas port contained by the gas block, through the gas tube, and back into the upper receiver to cycle the next round in your magazine.

Rail Height Gas Block

Rail Height Gas Block

Low Profile Gas Block

Low Profile Gas Block