AR 15 UPPERS FOR SALE
AR 15 UPPERS FOR SALE.
Barrel: 16″ Parkerized
Caliber: 350 Legend
12″ KeyMod Super Slim Free Float Handguard
5.56 Mil-Spec Bolt Carrier Group AR-15 Nitride C158
While both have their good and bad points, I prefer the AR series for a couple of reasons. One being, the M16/M4 is the standard battle rifle for the U.S. Armed Forces and federal, state, and local law enforcement.
In most cases, parts for the M16/M4 are interchangeable with the AR-15. This means that when SHTF, you will find parts, magazines, and ammunition anywhere.
There are differences between the military and civilian versions of the rifle. We’ll talk about those, as well as the differences found among the AR family of weapons.
Before we get into the AR-15, I feel it’s important to know a little bit about the M16/M4 and its history.
Semi-automatic AR-15s for sale to civilians are internally different from the fully automatic M16. On the outside, they appear almost identical. With the upper receiver only a little different (having an area milled out for clearance).
On the inside, though, they are apples and oranges, being the hammer and trigger are of a different design. The bolt carrier and internal lower receiver of semi-automatic rifles are different.
In fact, the firing mechanisms are not interchangeable. This was to meet ATF requirements so civilian weapons are easy to convert to full-automatic.
In the late 1970s and early 1980s, modifications to the AR-15 were rampant. That was with “Drop-In Auto Sear” or “lightning-link” conversions to fully automatic.
But, these were very straightforward modifications. And, unless using registered and transferable parts made before May 19, 1986, are now illegal.
In 1986, The Firearm Owners Protection Act (Public Law 99-308) redefined a machine gun. It was to include individual components used to convert a semi-automatic firearm to a full-automatic.
I cannot stress this enough. If you convert an AR-15 to fully automatic and you get caught, you are going to prison. The ATF’s Firearms Enforcement Division is very serious about this.
Having said that, there are parts that are interchangeable. Having them installed on your AR-15 does not make it a machine gun under federal law though.
The full-auto bolt and bolt carrier are interchangeable, and having one in your rifle is legal.
Parts of the AR-15 Rifle
One thing to note on the interchangeability of AR 15 parts, the AR-15 comes in two variants: Commercial and Mil-Spec.
Over the course of this article, I’ll point out the differences between AR-15 and M16/M4 parts and Mil-Spec vs. Commercial. Regardless, the various types function in the same way.
The AR-15 consists of three major components: the upper receiver, the bolt and bolt carrier, and the lower receiver. Two pins hold together the upper and lower receiver.
Pushing the rearmost pinout will allow the upper receiver to tilt forward for field cleaning. Pushing both pins out then will allow the upper and lower assemblies to separate.
There are two basic operating systems for the AR-15. Direct Impingement and Gas Piston, with the most common being Direct Impingement. All the ones I own are Direct Impingement.
Direct impingement is the original technology used in the M16 and its variants devised by Eugene Stoner in the ’50s. Propellant gas from the fired round goes through a small hole located in the barrel.
This gas is then channeled through a very small tube where it comes in contact (or impinge) to the bolt carrier.
At this point, the gas pushes to the rear of the rifle, forcing the bolt carrier back where the spent case comes out.
As the bolt carrier moves rearward it pushes the buffer back, compressing a spring.
It is then pushed forward by spring-loaded action and strips an unspent round from the magazine. After that, it goes back straight into the chamber of the barrel.
A gas piston is the same operation used by the AK-47. While it is more or less the same as direct impingement systems, there are a few differences.
Firing a round again feeds propellant gases into the barrel. But instead of going into a tube as it is in a direct impingement system, it stays in a separate cylinder.
This cylinder holds a piston. As the gas moves the piston, it, in turn, pushes the bolt carrier rearward.
Then it extracts the spent rounds and feeds in the new round. The bolt carrier pushes forward to the closed position by a spring, as with direct impingement.