The type of builds in AR 15 varies with the ammunition type. Therefore, the common parts will not be compatible with all types of the builds. The most common ar15 parts which are available in different varieties are enlisted below:
• The lower part of the receiver of AR15.
• The upper part of the receiver of AR 15.
• The kits that are related to the lower part of the receiver.
• The kits related to the upper part of the receiver.
• The extension that is mandatory for the lower part of the receiver.
• A buffer.
• A spring for the buffer.
• The system for blocking the gas and a barrel.
• The guarding equipment for the hands.
• The kit related to the carrying of the bolt like the pin for firing, bolt, carrier, spring, cam, extractor, and the ejector.
• The butt-stock which is collapsible in nature.
• A magazine for checking the limits and the capacity.
The main difference between the lower part of the receiver which is of the billet style and the lower part of the receiver which is of the forged style is that the forged type is prepared by the smashing of a metal when it is hot to compress the metal and make it durable and strong. For the billet type part of the lower receiver, are mechanized and prepared out on one block of the metal which usually has a greater custom and modified design to make the weapon look good. The guard for the trigger is also built in the billet form of the receiver and is immovable. The cost related to the billet type of the receiver is usually more than that of the forged type receivers. However comparing the capacity of the tolerance, the forged type is way much stronger and tolerant as compared to the forged type, however, none are considered to be weak.