In the new products section of the SHOT Show On Demand, the virtual version of the world’s largest arms exhibition, I came across this rather interesting AR-15 lower receiver made by the U.S. Arms Company (USAC). What makes the USAC M-4 CLS UTAW lower receiver unique is the built-in mechanism that allows applying tension and tightening the upper and lower receivers against each other.

Here is how the company describes the way this receiver tensioning mechanism works and the improvements it results in.

U.S. Arms has developed a revolutionary new device that improves barrel stability and accuracy through a secure fit, bringing the upper and lower receivers into proper alignment. This improves the accuracy of any AR-type firearm by securely transmitting torque through the lower receiver into the shooter’s shoulder and wrist.

High-speed video shows forward movement of an AR upper receiver and then a rolling motion induced by the bullet/barrel interface torque. This technology completely removes upper/lower loose fit by pulling rearward, preloading the front pivot pin, and pulling back and down on the rear take-down pin, which securely mates the upper receiver into the lower receiver bed.

This system allows the shooter to have the equivalent of a bolted together upper and lower receiver group while maintaining the ability to quickly and effectively disassemble the firearm in a traditional manner through a simple thumb lever attached to a cam shaft.

Testing reveals up to half an inch of Minute of Angle improvement with certain upper receivers when attached to the USAC M-4 CLS UTAW Lower Receiver. You will not find a tighter receiver on the market.

In the SHOT Show On Demand description of this product, the company calls this mechanism the Cam-Lock System and claims that the tight fit created by this tensioning mechanism rivals the tightness of stock to receiver fit of bolt action rifles. The external thumb lever, which is apparently rotated to apply and relieve the tension, is ambidextrous. This lower receiver is compatible with mil-spec upper receivers and works with direct impingement and gas piston systems alike.

USAC M-4 CLS UTAW lower receiver is currently available for preorder at an MSRP of $649. The estimated start of shipping is in 3-4 weeks. USAC currently does not ship this product to New Jersey, New York and California.

I’d really like to see an actual comparison test of different upper receivers used with standard mil-spec and USAC lower receivers. What do you think about this particular product and the various solutions of eliminating the receiver slack in general?

Pictures by U.S. Arms Company, www.usarmsco.com