Description
The CMMG 16.1" M4 .22 LR Barrel & Bolt Kit is one of the easiest ways to build a rimfire AR without buying a whole new gun. Instead of a drop-in conversion that shares your centerfire barrel, this kit gives you a purpose-built .22 LR barrel and a matched bolt group, so you get better accuracy and cleaner function than a typical conversion. Add a magazine and a compatible upper receiver, and you're set for cheap trigger time.
The barrel is a 16.1 inch M4 profile made from 4140 chrome moly steel with a salt bath nitride finish inside and out, which shrugs off rimfire fouling and corrosion. It runs a 1:16 twist with a .22 LR sporting chamber, wears a .750 carbine-length gas journal, and comes threaded 1/2-28 at the muzzle if you want to add a can or brake. The barrel sub-assembly ships with the M4 barrel extension installed and properly headspaced, so there's no gunsmithing needed to get it running.
What Sets the 22D7C6C Kit Apart
Because this is a dedicated setup rather than a conversion that piggybacks on your 5.56 barrel, you avoid the accuracy penalty that comes from firing a .22 caliber bullet through a .224 bore. Folks who run these report tight groups at 25 yards once they find ammo their rifle likes, and the whole thing is built around simple blowback operation.
Getting the Most From Your CMMG .22 LR Build
A few tips make a real difference. CMMG recommends a round-style hammer, since notched hammers can cause function hiccups, and 36-grain plated-nose bullets have proven to be the most reliable feeding choice. Rimfire runs dirty, so plan on cleaning more often than you would with centerfire. Do that, feed it decent ammo, and this kit turns into a low-cost practice machine that keeps you on the range longer for less money.
Key Specifications
- Manufacturer: CMMG
- Manufacturer Part Number: 22D7C6C
- Model: Barrel and Bolt Group Kit
- UPC: 815835013985
- Caliber: .22 LR
- Barrel Length: 16.1"
- Barrel Profile: M4
- Barrel Material: 4140 Chrome Moly Steel
- Finish: Salt Bath Nitride (inside and out)
- Twist Rate: 1:16
- Chamber: .22 LR Sporting
- Muzzle Thread: 1/2-28
- Gas Journal: .750 Carbine Length
- Overall Length: 24.5"
- Fitment: Mil-Spec AR-15 / Mk4
What’s Included
- 16.1" M4 profile .22 LR barrel with installed and headspaced M4 barrel extension
- Dedicated .22 LR bolt carrier group
Frequently Asked Questions
What do I need to complete a build with this CMMG .22 LR barrel and bolt kit?
You supply a Mil-Spec AR-15 upper receiver, handguard, gas system components, and a compatible .22 LR magazine. The kit covers the barrel and the matched .22 LR bolt group. Once assembled onto a standard AR lower, you're ready to shoot rimfire.
How is this different from a drop-in .22 LR conversion kit?
A conversion kit reuses your existing 5.56 barrel, which fires an undersized bullet through a .224 bore and gives up some accuracy. This kit is a dedicated .22 LR barrel matched with a .22 LR bolt group, so the bore is sized correctly for the cartridge. The result is better precision and more consistent function for a purpose-built rimfire setup.
What ammo works best with the 22D7C6C kit?
CMMG points to 36-grain plated-nose bullets as the most reliable feeding choice in these blowback .22 LR setups. Like any rimfire, it can be picky, so it pays to try a few brands and see what your rifle groups best. Higher-velocity plated rounds tend to cycle the action more consistently than bulk soft-lead loads.
Does this kit require gunsmithing to install?
No. The barrel ships with the M4 barrel extension already installed and properly headspaced, so it goes together like a standard AR barrel build. If you can assemble an AR upper, you can put this together with common tools.





Reviews
There are no reviews yet.