
Availability: In Stock
Current Stock: Out of stock
The CMMG Receiver Ext and Stock Kit Carbine Mk3 is a complete rear-assembly solution for .308 carbine builds, bringing together the essential components you need to finish a lower receiver. If you're assembling a .308 AR platform rifle from a stripped lower, this kit handles the buffer tube, spring, and stock in one package—simplifying the build process and ensuring compatible parts work together from the start.
This kit includes a 6-position receiver extension (buffer tube), the corresponding action spring, and a 6-position buttstock assembly, all configured for .308 carbine specs. The modular design of the stock means you can dial in the length of pull to match your shooting style, whether you're working in heavy gear or running minimal kit. The 6-position adjustment gives you flexibility without adding bulk.
CMMG has built a reputation for no-nonsense AR parts that work reliably in the field. This kit reflects that ethos—straightforward, functional engineering that lets you focus on finishing your build and getting to the range or hunting stand. Pair it with your choice of lower parts kit and a compatible upper to complete a .308 carbine that handles the way you shoot.
| Caliber | .308 Carbine |
| Receiver Extension Type | 6-Position Carbine Buffer Tube |
| Stock Type | 6-Position Buttstock Assembly |
| Brand | CMMG |
| Components Included | Receiver extension, action spring, 6-position stock |
This kit is configured for .308 carbine builds. The receiver extension and action spring are matched to .308 specs and will not function correctly in other calibers.
This kit provides the rear assembly and buffer system. You'll still need a lower parts kit (trigger group, hammer, pins, springs, and safety selector) to finish your lower receiver.
Yes. The 6-position buttstock assembly allows you to adjust the length of pull across six positions to fit your body mechanics and gear configuration.
This kit is built for .308 carbine specs. Confirm compatibility with your upper receiver and lower before assembly, as .308 AR platform variations exist.

SKU: 167525162 • Width: 6.75in • Height: 1.5in • Depth: 14.5in • Weight: 1.06oz
Availability: In Stock
Current Stock: Out of stock
The CMMG Receiver Ext and Stock Kit Carbine Mk3 is a complete rear-assembly solution for .308 carbine builds, bringing together the essential components you need to finish a lower receiver. If you're assembling a .308 AR platform rifle from a stripped lower, this kit handles the buffer tube, spring, and stock in one package—simplifying the build process and ensuring compatible parts work together from the start.
This kit includes a 6-position receiver extension (buffer tube), the corresponding action spring, and a 6-position buttstock assembly, all configured for .308 carbine specs. The modular design of the stock means you can dial in the length of pull to match your shooting style, whether you're working in heavy gear or running minimal kit. The 6-position adjustment gives you flexibility without adding bulk.
CMMG has built a reputation for no-nonsense AR parts that work reliably in the field. This kit reflects that ethos—straightforward, functional engineering that lets you focus on finishing your build and getting to the range or hunting stand. Pair it with your choice of lower parts kit and a compatible upper to complete a .308 carbine that handles the way you shoot.
| Caliber | .308 Carbine |
| Receiver Extension Type | 6-Position Carbine Buffer Tube |
| Stock Type | 6-Position Buttstock Assembly |
| Brand | CMMG |
| Components Included | Receiver extension, action spring, 6-position stock |
This kit is configured for .308 carbine builds. The receiver extension and action spring are matched to .308 specs and will not function correctly in other calibers.
This kit provides the rear assembly and buffer system. You'll still need a lower parts kit (trigger group, hammer, pins, springs, and safety selector) to finish your lower receiver.
Yes. The 6-position buttstock assembly allows you to adjust the length of pull across six positions to fit your body mechanics and gear configuration.
This kit is built for .308 carbine specs. Confirm compatibility with your upper receiver and lower before assembly, as .308 AR platform variations exist.
SKU: 167525162 • Width: 6.75in • Height: 1.5in • Depth: 14.5in • Weight: 1.06oz
