AR-15 Castle Nut and End Plate
The castle nut and end plate are two essential parts of an AR-15. They are situated on the end of the receiver and are necessary for the proper and reliable performance of your AR pattern rifle or pistol.
What Is an AR-15 Castle Nut?
Castellated nuts, also known as castle nuts are used in various items. They have notches on one end that give an appearance similar to the battlements of a castle, which is why they are called castle nuts. They are used to lock the nut in place so that it can remain in its position and resist vibrations.
Therefore, on AR-15s, a castle nut is used to join the buffer tube to the receiver. The castle nut keeps the buffer tube in place and resists the vibrations as the bolt moves back under tension from the buffer spring.
What Is an AR-15 End Plate?
The end plate is placed on the back of the receiver, keeping the rear takedown pin detent and spring in place, allowing your AR to function correctly. Moreover, the end plate also protects the rear of the lower receiver.
What Is a Properly Staked Castle Nut and End Plate Setup?
There are many things that AR-15 owners disagree on, and one of the biggest debates in the AR-15 community is whether you should or should not stake your End Plates into your Castle Nut. Some say stacking is essential to ensure that the castle nut does not come loose, whereas some say that staking is permanent and doesn't allow you to change your buffer tube or endplates easily.
The truth is that staking is a good habit, especially on service or competition rifles that are used frequently. All Mil-Spec AR-15s have staked castle nuts. However, staking isn't necessary if you occasionally use your rifle for shooting at the range or hunting.
Why Use Aftermarket Castle Nut and End Plate Setups?
Many manufacturers make aftermarket castle nuts and end plates for AR-15s. These parts have many features that make them better than standard AR castle nuts. Companies like PWS make a ratchet lock castle nut and end plate system, which allows you to have the stability and solid fit of a staked castle nut, and ease of removal of a non-staked castle nut. Such setups can be great for competition-shooting rifles.
Some aftermarket endplates also have QD sling slots, or loops, which are great for AR pistols, which don't have a stock. These endplates allow shooters to add a sling to their AR Pistol for carrying or to create forward tension while shooting.