Why AR-9 Ejector Alignment Matters
Unlike a standard AR-15, the AR-9 is a direct blowback system. Since there is no rotating bolt or built-in ejector to assist in kicking the brass clear, the function of the ejector is moved down into the lower receiver. The relationship between the bolt carrier groove and the fixed ejector in the lower is critical. If it’s seated too low, too high, or off-center, you will experience constant stovepipes or failure-to-eject (FTE) and potential magazine insertion issues.
The Installation & Seating Process
Tools needed:
Table or work surface
Blue loctite
1/8” Allen Key
Small frame Glock compatible magazine
Torque Wrench (Recommended)
Set Screw Torque Spec: 30-33 inch-lbs - NOTE: Do NOT mix this up with ft-lbs, as that will cause damage to the firearm.
Our DTT AR-9 lower utilizes a tuneable ejector held in place by two set screws. You can adjust your ejector using the following method:
Ensure the firearm is unloaded with the magazine removed. Place the gun on your work surface with the top of the upper receiver facing downward. It just needs to be stationary, not secured. If you have an optic or any accessories installed, you may want to remove them or find something to prop the gun up to make it easier to work on- cans of food wrapped in paper towels to avoid scratching is one convenient solution.
*If you ordered an unassembled lower and are using your own 9mm bolt, it’s a good idea to first test fitment by dropping the ejector into the bolt carrier slot to verify it slides in smoothly without binding. If your lower is assembled, remove both set screws to remove the ejector for this test.
In order to properly tune the ejector to the bolt, the easiest process is to have the ejector in a fixed position with the set screws snug just as it comes installed from us. The lower should be installed with the upper and the take down pins in place for a secure fit.
With the bolt closed, and the lower in place, loosen the set screws until the ejector drops into place. Your viewpoint is looking through the empty magwell. The ejector should rest lightly inside the bolt and it is ideal for it to be level on the inside channel of the bolt carrier. If it does not immediately drop, you can prod it with a long tool with light force. If it is pressed down too hard or uneven, the added friction could cause unnecessary wear and cycling issues.
Once you verify the ejector is seated correctly, fully tighten one set screw, then remove the other set screw and apply blue thread locker to the set screw and thread it back in, torquing it to the correct spec. Repeat for the second set screw. The ejector may move in this process, so be careful not to bump the firearm but the ejector should stay in place with one set screw always secured. Confirm fitment by racking the bolt back and forth. You should feel no binding and the ejector should look level. Insert a magazine. It should lock into place via the mag catch and not be able to over insert.
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