M508/308 info and instructions
Due to the variety of manufacturer’s, we cannot guarantee these will fit your combination of parts. We've listed the measurements and dimensions that we have found to work correctly
- the tail of the bolt must be approx. 2.17"- 2.2" in order for the bolt carrier to move the lever.
M508 lever and safety installation:
Take the included machine screw and lock washer and thread them into the lever using a 5/64" allen wrench. Loctite or other thread locker is recommended to prevent the machine screw from loosening up and backing out. Thread on the included spring onto the machine screw until it is snug against the lever. Your lever is now assembled.
PSA/DPMS lowers are slightly different than Aero M5/Stag10 receivers and require a shorter lifter spring, if you are using a PSA/DPMS type receiver set, the lifter spring will show deformation after hand cycling the action a few times. With a sharp pair of small wire cutters, cut off the first 2 or 3 coils of the lifter spring and check for deformation by manually cycling the action. If you are using an Aero M5/Stag10 lower receiver, the included spring should be the proper length and cutting coils shouldn’t be required unless the spring is deforming from use. If you need to remove or replace the spring, it will more than likely not come off without being damaged unless you unscrew the machine screw from the lever.
Install the Push Button Safety from the left to the right, with the keyhole slot entering the receiver first and facing up. With the Push Button Safety flush with the interior left hand wall of the receiver, place the lever into the receiver in front of the Safety.
The "tail" of the lever will be pointed to the buffer tube. If it is installed backwards, it will not function correctly.
Push the Safety into the receiver until the lever and Safety lightly touch and then align the keyhole slot with the lever by twisting the Safety into position. Once aligned, press the Safety all the way through the receiver.
While maintaining pressure on the Safety, roll the receiver upside down until the hole for the safety selector detent is facing up - insert the included detent rounded end first into the hole in the receiver. Twist/pull the Safety until the detent is correctly positioned in the detent slot on the Safety.
Install grip with the safety detent spring prepositioned inside the grip. Tighten screw until it stops. Test Push Button Safety - it should easily move between positions with enough resistance that it wont move unintentionally or by a slight accidental bump.
All the way to the right is Fire. All the way to the left is Safe. The middle position is Active Safety.
We advise against shortening or cutting the stock safety selector spring - our detents are manufactured to duplicate the OEM detent length.
M508 fitting and modifications:
The upper receiver will need to be modified to allow maximum movement of the lever. The slot/opening will need to be extended to the rear take down lug. A dremel will work if you're careful. You will need to cut the upper receiver until it is flush with the rear take down lug as shown.
We have redesigned the M508 lever in order to fit most AR308s, but the top of the lever might need to be lightly ground/sanded IF the bolt binds while manually cycling the action. The lever needs to fit inbetween the upper receiver and the bottom of the bolt carrier when the bolt carrier is in its fully rearward position.
With an assembled unloaded rifle placed in the safe position - start by hand cycling the bolt and IF the bolt binds, you'll need to either tap the muzzle against something firmly in a downwards motion to free the bolt or remove the upper while the bolt is partially retracted. Scraping or obvious marks in the cerakote finish on the M508 lever should indicate where the lever is making contact and where the lever will need to be lightly sanded.
High Shelf Lower Receivers:
Certain brands and models of lower receivers have a shelf behind the safety selector hole that is higher than the halfway point of the safety selector hole. If your receiver is a “high shelf” you will need to cut the portion of the shelf directly behind the safety selector hole to allow for the lever to freely move to its rearmost position. Using our push button safety assembly with a high shelf receiver that has not been cut to allow for the free movement of the lever may result in the lever being damaged or broken by the bolt.
We’ve found that a dremel carbide cutter will easily cut the shelf directly behind the safety selector and allow free movement of the lever.
To check if your lower has a “high shelf”, you will need to use a straight 1/8” gauge such as a drill bit or an allen wrench.
Lay the 1/8” gauge across the top of the lower receiver and the lever should be able to freely rest on top of the 1/8” gauge. Verify that it rests freely along both sides of the receiver and not just in the center.
Due to the radius shape of the shelf in some receivers, the lever has clearance when centered, but if the weapon is laid on its side such a shooting bench and then picked up and fired again, the lever may have shifted to the side and will now be obstructed by the shelf which may bind the bolt, damage the lever or in some cases forces the Safety into another position as the lever is forced towards the center.
