Product Description
If you're doing a 308 build you have to navigate a few tricky compatibility issues. You've got to figre out whether your barrel uses the older Armalite AR-10 length gas length, or the more modern DPMS spec. On Armalite AR-10 pattern builds, the gas journal is slightly forward compared to DPMS-pattern.
What length of gas tube do I need?
Take your barrel and measure the distance from the breech end overall to the gas block shoulder, in inches. Look up this number on the chart below.
| Distance to gas block shoulder | Gas tube size |
| 9 7/8" | 11.75" (AR-15 Midlength) |
| 13 1/4" | 15.125" (AR-15 Rifle) |
| 10 1/8" | 12 1/2" (AR-10 Midlength) |
| 13 1/2" | 15 3/8" (AR-10 Rifle) |
* DImensions are approximate
Maple Ridge Armoury, DPMS, and most brands follow the DPMS patterna and use AR-15 gas tubes.
Armalite, Anderson, and a few others use the old, longer tubes that are similar dimensions to the original AR-10.
You get:
- One gas tube of the chosen length
Compatible with:
- Standard AR-15/M16 gas blocks (regardless of barrel diameter)
- AR-15/M16 Barrels regardless of caliber
- Standard upper receivers
- Mil spec gas keys on BCG
- Mill spec and free float barrel nuts
- Mill spec gas tube roll pins
Installation Difficulty:
Tools required: It may help to have some needle-nose pliers and a pin punch to drive in the Gas Tube Roll Pin.
Installation notes: If you are replacing a Gas Tube, we recommend installing a new Roll Pin for factory-fresh retention strength.
