3D Printed Mini AK Airsoft SMG's
A while back I got the idea that in order to be more mobile on the field, I needed to lose some equipment weight. Gear and my fat rolls are all one thing, but losing weapon weight was another. Going for a lightweight platform should in theory help with travel endurance as well as make close quarters combat easier. Since I don't do half ass'd, I decided to full rambo and make two AK SMG's
The design standard was simple. Take what I knew to be an AK-47 (Version 3 gearbox, hopup and AK Mag) and make it really small. No stock, short barrel, lightweight. I ended up gutting two CYMA CM028's for the project as they were dirt cheap and reliable platforms. Prior experience told me that compared to other purpose built SMG's on the market (MP5, TMP, etc), using a full V3 gearbox and running gear should make for a more easily upgrade-able platform down the road.
Laying out the AK-SMG internals was relatively simple. I would be using roughly the same geometry that the AK47 employed. Having the mag latch integrated into the trigger guard and gearbox mounting handle reduced the number of components I needed to design for myself.
Starting from scratch was a daunting task. Since the model needed to be 100% accurate, some 3D printed test dummies were used to dial in the model. The two top prints pictured above were solely for test fitting the gearbox - hopup - magazine.
The first functioning prototype was nicknamed "The Pepperbox". Everything was enclosed and followed my initial vision as I was drawing on the MAC10 for inspiration. The battery was slotted into the upper housing.
The first test run was a success to some degree of the word. Pepperbox was indeed rugged... but heavy. Walls were needlessly thick and a missed dimension ultimately resulted in the rearward 3D prints cracking.
Learning from the first design, I went back and did some reductions. Moving the battery outside of the body and reducing wall thicknesses were huge benefits. I realized having a full length picatinny rail was highly unnecessary.
Better! More streamlined and more unique than before. The display on the back was a volt meter I found in my junk pile. Testing out to see if reading the voltage was worthwhile... turns out not so much on the lipo batteries.
After sitting on the design for a couple days wondering where to go from there, I had an epiphany. Since I regularly clean my guns and my local field typically doesn't have me wading through feet of mud, exposing the gearbox might not be a bad idea. It would reduce more mass, reduce print times and aid with cooling.
The results were as shown. The final design resulted in 2 half shells, a rail mount and the picatinny rail. These would be the last models I used Wood PLA prints. The stuff is great for prototypes but not strong enough for a battlefield. Final prints shown in the first image were PETG.
After a number of matches played this summer, I'm happy to say I'm very pleased with the results. While playing with dual SMG's introduces some reloading speed issues, they were nonetheless fun. In the end I started tossomg the second to a friend and just ran one. On target times dropped and despite the short barrel, accuracy really didn't seem to be too hampered over the stock CM028. I ended up losing around around 50-75 fps due to the barrel length but in close quarters, the difference is negligible.
For next year I'd like to improve on a couple aspects. The biggest being battery protection. Covering the battery from incoming BB's is a must as spontaneous Lipo fire is not on my agenda. The other would be covering the rear. While I know I went uncovered for reasons, in the end I think I could revise the design once more with a cover that didn't negatively hurt print complexity and build times.