Quarter Circle 10, THE AR Pistol Caliber BRAND. Leader in top of the line, dedicated AR15 Pistol Caliber parts. 9x19MM Barrels
Shipping: All orders are shipped within 72 hours Monday -Thursday 6am - 4pm Arizona Time.
Any order containing a lower receiver will not be shipped until we receive a copy of your FFL. Once received regular shipping policies apply. Submit your FFL Here.
Returns: Quarter Circle 10 offers a 30 day return, refund and exchange policy. See Details.
Proprietary Feed Ramp, contoured specifically for 9MM ammunition, ensures feed reliability and increased ammunition compatibility.
Available in 3.5", 5.5", 7.5", 10.5" and 16" Lengths.*
4150 CMV Steel
1-in-10″ twist rate
QPQ Nitride Treated
Quarter Circle parts are designed to work within mil-spec perimeters. However, for optimum performance we recommend using QC10 parts for all your core elements, (Receivers, Bolt, Barrel and Adjustable Buffer System).
Made For - Not Modified. Every QC10 product is engineered specifically for pistol caliber ammunition, not modified from an existing platform, increasing functionality, reliability and overall performance.
*Barrels are measured from the end of the muzzle to the end of the breech/feed ramp. Approximately1” of the barrel rests inside the upper receiver upon installation, resulting in an installed length of 1″ less than listed overall length.
*The installation of a pistol-caliber suppressor requires the use of a fixed barrel spacer. See your suppressor manufacturer for information on the requirements of your particular model.