Polymer AR lowers have something of a bad name, but is it deserved? In collaboration with Russell Phagan (www.SinistralRifleman.com) and GWACS Armory (www.GWACSArmory.com), we took a CavArms MkII polymer lower and put it through a series of increasingly harsh tests at a 2-Gun Action Challenge Match. Polymer has some very different material properties than aluminum, and we wanted to see what it could handle. We were also testing a set of Hahn Precision backup iron sights to see if they would hold zero through the various tests.
We started with a simple drop test, followed by using the buttstock to break some 2x1 boards, doing pushups on the rifle, running it over a couple times with a Jeep, and finally shooting several rounds through it with another rifle. After each test the rifle was run through a stage of the match by Karl and Russell, with no maintenance other than replacing the recoil spring that took a bullet. Through the whole test the rifle had only one malf (which was a bad cartridge), and the Hahn Precision irons stayed zeroed well enough to make 200-yard hits.
The key to the durability of the CavArms receiver is that it was designed from the ground up to be made of polymer. The areas where a standard AR receiver is too thin for polymer (like the buffer tube attachment point) were significantly increased in mass so that the polymer could support the stresses on the gun. The result is a lower that can withstand damage that would render an aluminum lower unusable, while also being lighter than an aluminum lower assembly. What more could you want?