The AR15 rifle, which is very similar to the M16 rifle or the M4 rifle, consists of two major parts that are commonly referred to as the Upper and the Lower receiver. In this article we will describe the parts of the Lower and how it is used in the AR15 with semi automatic fire.
The AR15 complete Lower consists of the lower receiver, trigger group, pistol grip, buttstock, buffer tube, buffer, buffer spring, trigger guard, lower receiver parts kit.
- The Lower – The AR15 lower is the only part of the AR15 rifle that is stamped with a serial number. Only a person that can legally own a gun can purchase an AR15 lower. There are two descriptions for lowers, one is the stripped lower that only has the lower, and the other is the complete lower that includes all the parts listed above. The lower can be built of many different materials such as aluminum, plastic, and steal. The most common material is aluminum.
- Trigger group – The Lower includes the trigger group, there are many different designs of trigger for the AR15, and they very in price, parts, trigger pull poundage, shape of the trigger, etc. Care needs to be taken when putting in a trigger group, I have personally have had to fix trigger groups that have been installed by professional full time gun smiths. The most common issue is putting in the springs in backwards. Adjustments can also be to the trigger group to allow for a smoother trigger pull, these adjustments are easily performed but should only be performed by a certified gun smith.
- Pistol grip – although you can make an AR15 that does not have a pistol grip, this is a default design of the AR15. There are many different shapes of pistol grips, I would recommend looking around and trying a few, I am not a big fan of the standard A2 pistol grip.
- Buttstock – Like the pistol grip there are many different designs for the buttstock, the most common are the A2 style solid buttstock and the M4 style 6 position adjustable buttstock. The buttstock is there to help you steady your rifle for accuracy but it also holds the buffer tube.
- Buffer tube, buffer, buffer spring – The Buffer tube is part of the buttstock and as the rifle is firing this is where the carrier will go as the gas pushes it back after a round is fired. The carrier will hit the buffer that has a large rubber pad to slow the carrier and the buffer spring also slows the carrier but then will push the carrier back into position.
- The Lower receiver parts kit – this kit comes with all the small springs, detents, trigger guard, etc. To take a stripped lower and make it a complete lower – less buffer tube, buffer, buffer spring, and buttstock.
Here is a great book to aid in assembling an AR15: Build Your Own Ar-15