Point muzzle in safe direction. Engage safety if not already engaged. Drop magazine. Pull slide back and lock back to ensure that pistol is unloaded. Using your finger or a stick/pen/pencil, push ejector (mounted in frame) down (the ejector should pivot forward and down). Now, push the slide stop from left side of frame to the right (no need to push it all the way out of the frame). Pull slide back, lift up and separate from frame. Remove recoil spring guide rod and recoil spring assembly. Remove barrel from slide. Basic field stripping is now complete.
Don't forget to call Ruger Customer Service for a free copy of your manual.
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