Since I picked up my first in 2005, I keep my guns quiet whenever possible. Call it a silencer, can, sonic reducer or whatever you please: just don’t catch me at the range without one. Flash suppressor? Muzzle brake? Nope, a suppressor. When it came time to choose a muzzle device, I had to go with my favorite. The handguard supplied by QC10 has an anti-rotation horseshoe, that indexes on the (non-present) gas tube. I slid the handguard onto the barrel nut, aligned the top rails and used the pair of clamps (with Loctite) to affix the handguard to the nut.

I still installed it to prevent an unsightly gap.

The upper receiver of the QC-5 is even easier to put together. Simply place the barrel into the upper, apply a little dab of Loctite to the barrel nut threads and torque it down. Just a small precaution: hold onto it when torquing! There is no gas block, gas tube or ejection port door to be concerned with on the QC-5. While I used a receiver block, the QC-5’s unique interior geometry meant that I couldn’t use the block’s pins to hold the receiver in place. Was waiting for an oversized one, ended up using the stock one. Finished, minus putting the bolt catch back in. Finished, the lower looks great! We still have the buffer spring and weight to cover in an upcoming section. The grip is held by a single screw, while also holding in place the safety selector, detent pin and spring. These shortened pins hold their respective assemblies together and align until you slide the permanent pins in through the receiver holes. The trigger assembly and grip are pretty “drop-in”, especially with the use of Geissele’s trigger and hammer pin placeholders. The rear takedown pin is much easier, and its related spring is held in place by tightening down the receiver extension of the SB PDW brace. This reduces my pin-launching events by about 99%.

I like to use a flathead screwdriver to hold the detent pin in place until the takedown pin can slide over it. Installing the front takedown pin can be a little frustrating for those who aren’t dexterous. It ended up having reset issues and was swapped for an ALG Defense ACT trigger. Side note: the Geissele S3G wasn’t on the “approved trigger” list by QC10, which means it was a known risk going in. I used a Geissele Super 3 Gun (S3G) trigger, SB Tactical PDW brace, Mission First Tactical Engage pistol grip and a few assorted extras to finish the parts list. That leaves the trigger assembly, takedown pins, grip and receiver extension.

Fn 9mm carbine side charging upper