Make sure the rifle is completely unloaded with magazine removed. With proper size screwdriver, loosen stock screws, center safety, and remove stock. With a 3/32 punch and mallet, push or tap out the two trigger guard assembly cross pins and remove the trigger guard assembly.
 

Push or tap out ejector pin and remove ejector. Push or tap magazine latch pin just clear of the bolt lock. Remove the bolt lock while the magazine latch pin holds the magazine latch captive.

Release the hammer by squeezing the trigger and gently allowing it to pivot forward. Push or tap out hammer pin and remove hammer, along with two hammer bushings and the bolt lock spring.

Replace the Ruger bolt lock spring with the supplied auto-bolt lock spring. Place the new spring on the right hammer bushing with the red colored leg up. Place the hammer with hammer bushings and new spring back into the trigger guard assembly and push in the hammer pin. The hammer strut must mate inside of the rear slot of the hammer correctly. Once the hammer pin is in place, cock the hammer to hold the hammer strut captive.

Place the new auto-bolt stop into the trigger guard assembly inserting the red colored leg of the auto-bolt stop spring (installed in step 4) into the hole located through the flap extending from the auto-bolt stop. The bottom portion of the auto-bolt stop is the manual bolt release tab and should extend out the bottom of the trigger guard assembly while the spring loaded ejector should locate in the ejector slot. With the new auto-bolt stop fully inserted, push in the magazine latch pin capturing the auto-bolt stop. You may need a good light source, (such as a flashlight) to verify that the bottom leg of the auto-bolt stop spring rests in the pocket where the safety is located. Once installed correctly, the auto-bolt stop will pivot freely on the magazine latch pin with pressure exerted from the auto-bolt stop spring pivoting the device forward.

Reverse the procedure in step 1 to reassemble the rifle. REPLACE THE FACTORY RUGER MAGAZINE WIH THE SUPPLIED CST MODIFIED MAGAZINE. Test proper functioning of the auto-bolt stop by inserting the supplied CST modified magazine and pulling the bolt rearward. The bolt should automatically stop upon its completed rearward travel.