I have a Ruger SR1911 born on 1-15-2015 and have 500 rounds through it. I decided to field strip and clean however I had a problem with re-assembly. When I tried to replace the slide stop (part #23) the detent of the stop hit the pin rod that runs from the slide stop to the firing pin safety. I could not snap it in as instructed in the manual. I called and talked to Josh a technician at Ruger and he explained how to do it. When the slide is put into place you will hit the pin and not be able to push the slide stop (#23 in your manual) in. The safety pin which is housed in a rail and has no part number and will inhibit the reinstallation of the slide stop. You have to depress the safety pin in with your finger nails or a very thin blade until you get on top of the slide safety detent. Remember clearance is very, very tight. When the pin is on top of the detent on the slide stop then push harshly until the pin goes into the detent. The safety pin consists of a rod on each end and a spring in between them and they have strengthen them to help keep the slide assy tight against the frame. The latest Rugers have a very tight tolerance and you will find that the slide is very tight against the frame. When you shake the pistol, you will NOT hear any rattles as some have stated and that's due to the safety pin protruding into the slide stop detent. It takes some practice and maybe a little help from a friend with a sharp finger nail or a very thin blade inserted between the slide stop and the safety pin, however it can be done.