Cosaint Arms COS21 Compact 10 mm – Chunk-Ported, Optic-Ready 2011
This COS21 is a true boutique 2011-pattern pistol: officer-length slide and barrel, double-stack 19-round 10 mm firepower, and a hand-fit steel frame. Factory “Chunk” ports in both barrel and slide tame muzzle rise, while the C&H optic cut keeps your choice of micro-dot low and co-witnessed with the green fiber-optic front blade. A crisp 3.5 lb flat-faced trigger, skeletonized commander hammer, and aggressively milled 7075-aluminum grip module complete a package that blends carry dimensions with competition-grade performance—something rarely seen in a factory-built 10 mm 2011.
Condition
Very good overall. Light, superficial handling marks and minor blemishes on the grip module are the only signs of prior use. Slide-to-frame fit remains tight, controls are positive, and function checks perfectly. Bore is immaculate—mirror finish with sharp, unworn rifling.
What’s Included
• Cosaint Arms branded hard case
• Factory cable lock and owner’s packet
• Two MBX stainless 19-round magazines with extended aluminum base pads
• Spare Fusion Match threaded 10 mm barrel (knurled protector included)
The COS21’s compact 3.5" bull barrel makes it one of the few officer-length 10 mm 2011s available today. Cosaint’s signature porting vents gas upward through four squared “chunks,” noticeably flattening recoil impulse in a cartridge known for authority. Prefer a suppressor or compensator? Swap in the supplied match-grade threaded barrel and you’re ready—no gunsmithing required.
The modular 7075-aluminum grip can later be exchanged for alternative aluminum colors or even a polymer frame, keeping the serialized steel receiver intact. Diagonal front and rear slide serrations, a flat trigger with short over-travel stop, and tuned MBX 140 mm magazines show clear competition lineage, while left-side thumb and grip safeties plus an inertia firing-pin block satisfy duty-carry expectations.
Hand-built in North Carolina, each COS21 reflects Cosaint’s “to protect/defend” Gaelic namesake: reliable, accurate, and crafted in limited numbers attractive to collectors following emerging American 2011 makers.
If you’ve been searching for a compact, ported, optic-ready 10 mm with custom-grade fit and factory support, this COS21 deserves a slot in your range bag—and very possibly your daily carry rotation.