The design of the AR 15 allows the end user to build a multitude of different firearms. This is done by just changing the upper receiver to the new calibre. Several of the different Calibre options use the same magazines, and only require a different calibre of ammunition to be loaded, to match the new upper receiver unit
One lower can be use with several uppers to make different rifles, a lot of these options even share the same Bolt Carrier Group (BCG). Common choices are .223, 5.56, 6.5 grendal, and 300 blackout.
Here is a basic lower unit. This is the registered portion of of the AR rifle. It can be converted in the field very quickly. You will also see that this is where the Magazine used to hold ammunition connects to the AR Platform Design.
The pins that are in the lower receiver, that hold the upper receiver on, are shown here:
This platform also does a lot of Pistol Rounds including; .22 LR, 9mm, 45 ACP, and .458 SOCOM. It is a very versatile design, that can be built many ways. Pistol uppers are quite common.
This is a 5.56 upper unit and you can see the two holes at the top of the picture that match the two retainer pins in the lower receiver. it also contains the Bolt Carrier Group (BCG) and the forward assist with the bolt used to cock the Rifle. This piece is Calibre specific, and it is the part changed to switch the Calibre. This portion is NOT registered, and you can mail order this piece, because it is simply a part, and not a Firearm.
The AR-10 is a very similar design that handles a longer round. It is primarily in 308, but will also handle a longer 6.5 Creedmoor, and the new 6.8mm which shows major promise for the future of this platform. The AR-10 assemblies look like the AR-15 assemblies, just slightly longer where the Magazine attaches.
Quote of the day: "AR-15s are like LEGOs for grownups." -Anonymous
When you have the finished Rifle, you have the means to defend yourself; but you still need a Plan! on how to defend you and yours! Here is the simplest plan I have ever seen:
“Be polite, be professional, but have a plan to kill everybody you meet.”
General James N. Mattis
The single best use for an AR-15, is not self defense (with the .223, or the 5.56mm round is way too small); but it is VERY good for Pissing off liberals! For this alone, everyone should have at least a dozen, ROFLOL! It is a good kids training rifle, and good for target practice, as the ammunition is lower cost than heavy rifles. It is a good learning tool, and shooting learned on an AR, transfers well, directly to heavier weapons.
Here is an angle on the AR-15 that many people have not considered. In the unconscionable attacks on innocent people by those feeling they have the right to harm others...the AR-115 platform saved lives. The base round used is a 22 calibre 55 grain pill. If these Evil people had used a Firearm with a decent round (ballistically speaking), we would have lost a lot more good people! The AR-15 round is so light that it wounds more often than kills; so if they manage to ban this firearm, more innocent lives will be lost, for certain!
Making laws, in ignorance, will always have misunderstood consequences; and the actual results are usually very bad!