Tech Note

July 8, 2000

TECHNICAL NOTE 40: Installing the AR-50 Scope Base

BACKGROUND: ArmaLite's Telescopic Sight Base is designed to be precisely yet easily fitted to the rifle's receiver. The base features a top surface bearing a MIL STD 1913 Picatinny Rail (which is actually A "Swan Rail" originally designed by Dick Swan of A.R.M.S.) and a bottom surface that bears two recoil lugs and two bearing pads.

Two bases are available: one with 15 and another with 50 minutes of slope built into the bases to allow shooting at up to 1000 or 1500 yards, respectively, using standard rifle scopes.

The AR-50 scope base uses unusually large anchor screws. In addition, the ingenious design of the base keeps recoil loads from stressing the screws and possibly shearing them off. The recoil lugs of the base, engaging the recoil slots of the receiver, take all such loads, and the screws are only used to hold the base against the receiver. The ArmaLite base is designed to assure a flat rail interface for the scope rings or mount.

INSTALLATION INSTRUCTIONS:

1. First things first: place the safety to the safe position. Open the bolt and inspect the chamber to make sure that the rifle is unloaded.
2. Set the T rails of the base into the T slot in the top of the receiver. Insert all four base screws and tighten them lightly. There should be a gap between the top of the receiver and the flat bottom of the base.
3. Open the bolt and feel for the mount screws protruding into the receiver.
4. Remove each screw in turn and shorten it to eliminate the protrusion, then replace it.
5. Tighten the two end screws until the gap under the mount just barely starts to close. Back off if the top of the rail distorts. Repeat with the two inner screws.

The design of the AR-50 scope mount controls recoil forces completely, without over stressing the mount screws.

MAW

Copyright © 1999 ArmaLite, Inc.