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Quarter Circle 10 Colt 9mm CLT9MM Lower Receivers

This is our Colt 9mm SMG dedicated lower. It is a purpose built platform for shooting 9mm SMG magazines. In the 1980s Colt started manufactuering a version of the M16 that used a direct blowback operation system to fire the 9×19 Parabellum round. Our CLT9mm lower is designed with not only operation in mind but aesthetics. It looks like it was made to shoot these magazines not just a regular AR15 magwell with a skinny magazine installed. Our lowers utilize a bolt hold open feature that no longer requires the use of a 9mm long finger bolt catch and uses a standard bolt catch.

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The Quarter Circle 10 Colt 9mm lower receiver is, quite simply, the finest pistol-caliber AR platform available. Precision milled from 7075 billet aluminum, each one of our receivers is hand-inspected at every stage of manufacture to ensure precision and quality. This is no poorly milled adaptation made from surplus AR-15 receivers. Our CLT9mm lower was designed from conception as a dedicated pistol-caliber receiver built around the Colt 9mm Submachine gun magazine. The Colt 9mm receiver is up to the task of delivering rounds on target with more accuracy and power than a handgun, all in a package that is tighter and easier to control than a rifle-caliber firearm. Form and function play equal roles in our design, and the CLT9mm not only runs like clockwork, it looks the part. With a simple yet distinctive aesthetic, the CLT9mm lower immediately draws attention, but also fits right in among other tactical weapons.

Just as in the lawless days of the American West, when having a rifle and a pistol chambered for the same ammunition made sense to lawmen, cowboys, and outlaws alike, today many officers of the law and private citizens recognize the advantage of running the same ammunition in both their primary and secondary weapons. The Colt 9mm lower carries this idea forward with our simplest, most traditional design. This simplicity and dependability is only part of what makes the GSF an obvious choice for tactical applications, home defense, or emergency situations.

Now, you can build your pistol-caliber platform with the peace of mind of knowing that every component is of the highest quality. Whether for home-defense, law enforcement, competition, or plinking, Quarter Circle 10 has you covered, with our philosophy of Made For- Not Modified. Each of our parts is engineered and manufactured with pistol calibers in mind, rather than modified from rifle-caliber components as an afterthought. We’re Quarter Circle 10, the AR Pistol-Caliber brand.


  • 11.5 oz stripped weight
  • Last Round Bolt Hold Open, ejector and all proprietary parts installed
  • Accepts all Colt-style 9mm Magazines
  • 7075-T6 Aluminum
  • Accepts mil-spec receiver extension (buffer tube)
  • Type III Hard Coat Anodizing
  • Billet Machined
  • Bullet Pictogram selector on both sides
  • Upper Receiver Tension Screw Slot (Screw Not Included)
  • Proprietary bolt hold open feature, no “long-finger” BHO needed

FFL Required Before Shipping. Please have your dealer email their license to or they can also fax it in.



Additional Info

Additional Info

Manufacturer Quarter Circle 10
Finish No
Barrel Length No
Caliber 9mm
Configuration No
Option No
Gas Length No
Height No
Rail Length No
Mount No
Profile No
Reticle No
Co Witness No
Size No


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