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The CMMG Low-Profile Gas Block is built for AR-15 barrels with a .625 inch gas journal, which is the size you typically find on pencil and lightweight contour barrels. It sits low enough to clear a free-float rail, so you can run a slim handguard that fully covers the gas system and reaches closer to the muzzle. Machined from 4140 chrome moly steel with a matte black finish, it holds up to the heat and pressure of a running direct-impingement gas system without complaint.
This is the part a lot of folks reach for when they strip off a factory A2 front sight tower and switch to a modern setup. Pull the old sight base, drop this block on, and you have room to slide a one-piece rail right over the top. It mounts to the barrel with two set screws that thread in from the bottom, and CMMG includes those screws in the package. For the most secure hold, dimpling the barrel under the screws and adding a dab of thread locker is the way to go, since set-screw blocks can walk under recoil if they're just snugged down.
Double-check your barrel's gas journal before ordering. Most standard AR-15 barrels run a .750 journal, so this .625 block is specifically for the thinner barrels. Getting the block's port lined up dead-on with the gas port drilled in your barrel matters a lot, because poor alignment leads to gas leakage and cycling headaches. One thing worth knowing up front: the gas tube roll pin is not included, so grab one with your gas tube if you don't already have it on hand.
CMMG has a long track record making AR platform parts and complete rifles, and this block reflects that experience. It's a straightforward, well-machined piece that gets a lightweight build looking clean and running right.
It fits barrels with a .625 inch gas journal, which is common on pencil and lightweight contour barrels. Most standard AR-15 barrels use a .750 journal, so measure your barrel at the gas block seat before ordering. If your barrel is the thinner .625 size, this block will slide right on.
It ships with the two set screws used to mount the block to the barrel. The gas tube roll pin is not included, so plan to pick one up with your gas tube. Basic hand tools and an Allen wrench are all you need for the install.
Yes, that's exactly what the low-profile design is for. It sits low enough to clear a one-piece or free-float rail, letting you run a full-length handguard that covers the gas system. This is the go-to move when swapping out an old A2 front sight tower.
Set-screw blocks can walk under recoil and heat if they aren't secured properly. Dimpling the barrel under the set screws gives them a positive seat, and a bit of thread locker helps them stay put. Take your time aligning the block's port with the barrel's gas port, since good alignment is key to reliable cycling.
| UPC | 815835012780 |
|---|---|
| Manufacturer | |
| Manufacturer Part Number | 55DA3AC |
| Color | Black |
| Length | 4.5500 |
| Model | |
| Product Type | Gas Block |
| Shipping Weight | 0.045 |
| Style | Low Profile |
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