See Updated Revision here

AR-15 Multi Caliber Speed Loader / Unloader - Free 3D Print Model - MakerWorld

This is a new variation of my previous v2 and v3 ar15 mag speed loaders!  the previous versions use a lever to push the rounds into your magazine, this uses a straight plunger to do the action, rather than rocking the rounds in, you pop them in.  The mag catch has been redesigned to be a snap fit together and eliminate the need for the 4mm bolt.  It still uses the same spring as the v2 and v3 which is approximately, ¼" diameter by about ¾" long.  If you printed the v2 or v3 that spring will work in this.  I have tried it without a spring, and it still works but you'll have to hold it with your palm to retain the mag. To assemble, insert the mag catch into the body, insert the spring over the catch shaft, then press and snap the catch button over the tabs.  once on you may need to push the catch shaft back to free it and allow the spring to keep them apart.  works great!  The loader needs 2 m3 by 20mm screws threaded up into the lower trigger part, insert that part through the body and finish screwing them into the top trigger part.  You'll see 2 additional holes in both the body and upper trigger; those ate for additional 3mm screws.  The intention was to use pen springs to help with the trigger lift, but they don't benefit the tool, so I removed them.  Like my other versions this has been tested with both steel and polymer mags.  

See Updated Revision here

AR-15 Multi Caliber Speed Loader / Unloader - Free 3D Print Model - MakerWorld