9mm STEN Magazine Conversion on an AR-15: Build Your Own Custom Homemade Mag-Block
By Paul Groves of High Powered Armory
It is no secret that nowadays the price of ammo has made shooting your guns more painful than the cost of the actual firearms themselves. Remember when 22 ammo was the cheap alternative to back yard fun? With the price of 22 ammo into the double digits and the cost of 5.56 making your AR-15 more of a collector’s item than a weekend toy, many have been seeking cheaper alternatives to shoot their AR-platform rifle. AR-15′s chambered in 9mm have been increasing in popularity due to elimination of affordable 223 and 5.56 ammo.
Even with the affordability of 9mm ammo, AR-15 enthusiasts have been turned off by the lack of options in design and function of 9mm AR-platform rifles. Recently, we found an affordable alternative to the costly dedicated and conversion 9mm’s that are out there .
We started out with a factory Olympic Arms upper (with bolt ) that we acquired through a private seller. Those who are unfamiliar with a 9mm conversion need to understand how it actually works. The extractor that is required on the standard Rock River Arms upper, or many of the newer companies, require a mag block that accepts Uzi magazines and has a built in extractor. This alone can cost over 200 dollars. Also, the cost off Uzi magazines is very high, usually running upwards of 30 dollars a piece. Now, with some very basic machining skills, you can actually build the same mag block that we did for around 15 dollars. This mag block allows the use of more affordable 9mm STEN magazines instead of the standard Uzi.
As you can see in the photo, this custom block has a small notch that snaps into the mag catch along with a small milled slit up the middle. The STEN mags themselves only require the drilling of a small hole, drilled and tapped with a small Allen screw as pictured. The average 9mm AR-15 setup can run you upwards of 1000 dollars in today’s market. We threw this entire setup together for under $550.00 dollars. That is including all of the mags. So, with everything working against gun enthusiasts these days, show some ingenuity, and build one for yourself.