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U.S. Arms Cam-Lock Lower Receiver

The USAC M-4 CLS Cam-Lock UTAW Lower Receiver improves the accuracy of any AR-type firearm.
This is a stripped lower receiver. Includes trigger guard.

ATF regulated items have restrictions and requirements:

  • Your order will ship only to a Federal Firearms License holder.
  • We are not currently shipping to CA, CT, DC, HI, MD, MA, MN, NJ, NY, or VA.
  • Please be sure to contact your local FFL dealer prior to placing your order to ensure they are still accepting transfers. Some FFL dealers are not open due to Covid-19.
  • Customer must read, understand, and agree to customer terms and conditions.



U.S. Arms has developed a revolutionary new AR-15 lower receiver that improves barrel stability and accuracy through a secure fit that brings the upper and lower receivers into proper alignment. This improves the accuracy of any AR-type firearm. Our patented U.S. Arms Cam-Lock Lower Receiver enables the tightest receiver fit on the market.

The U.S. Arms Cam-Lock Lower Receiver mechanically locks the upper and lower receivers together preventing the upper receiver from moving independently when the gun is fired. Most, if not all, AR-15 style rifles have significant play or “wobble” between the upper and lower receivers. Cam-Lock is what the name infers; a locking system. Cam-Lock is superior to “wedge systems” that push the receivers apart and out of alignment. Cam-Lock locks the mating surfaces of the upper and lower receiver together eliminating any play in the receiver set.

Cam-Lock is a mechanical way of what gunsmiths do to “BED” a rifle’s receiver in a rifle stock. 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.

The Cam-Lock Lower Receiver is the perfect base for your AR platform with an unmatched fit to upper receivers. It also comes equipped with a built-in oversized trigger guard to allow room for a glove. The high quality hard coat anodized finish of this receiver allows for corrosion resistance, easy upkeep, and fade resistance to ensure your AR is operational for years to come.

Testing reveals a minimum improvement of a 40% increase in accuracy over a mil-spec print lower receiver. The U.S. Arms Cam-Lock Lower Receiver, provides a vast improvement for your firearm’s accuracy. You will not find a tighter receiver set on the market, which is why we claim that we are “Home of the World’s Tightest Receivers”.

Compatible with all Mil-Spec upper receiver groups.:

  • AR-15
  • M-16 A1A2
  • M4









8.25 oz


Flat Dark Earth, Anodized Black

Product Benefits

Mechanically beds the upper receiver and lower receiver together.

Details and Build Materials

All U.S. Arms lower receivers are machined from a single billet of 7075 aircraft grade aluminum for added strength and durability.