AR15 Single Shot Magazine with lockback

thingiverse

This is a Single Shot AR-15 Magazine designed to load the AR one round at a time. It's perfect for testing rounds that won't fit in a standard magazine or eliminating variability when testing new loads. Insert the magazine into the magwell just like you would with a regular magazine. Pull the bolt back until it locks, then place the bullet on the trough and slide it into the chamber, or let the bolt slam forward to insert the round. Fire the weapon and the round will be ejected; the bolt will lock back. To print this design, use 25% infill for the main body and 100% infill for the lock and bar. Clean up these parts so they slide smoothly. Assembly requires a spring with a 3.5mm outer diameter. Place the spring in the pocket and test fit the lock; it should be flush with the top of the rib. Trim the spring as needed to achieve plenty of tension on the lock, then insert the bar through the hole. -----------------------***UPDATE***------------------------------- Initially, a single spring wasn't enough to keep the bolt locked back, so I added a dual spring setup. This requires the dual spring body and dual spring lock. Additionally, I designed a 5" long body with a dual spring setup for competitions that demand a 20 round magazine look-alike, as requested by aboxman in the comments.