1911 Problem after converting Series 80 to Series 70

[Old Salt]

After removing the Series 80 parts and putting in the Series 70 shim I started having the following problem. With the magazine installed, when thumb cocking the hammer it won't catch. Rack the slide and the hammer locks back but won't fire unless I drop the magazine. It appears the grip safety is involved. It appears the grip safety stays depressed unless I drop the magazine. What can cause that? Any ideas?

 

[John from MD]

With the magazine out, do the following.

1. Rack the slide then, without touching the grip safety, put the manual safety on. Ok, got to 2.
2. Take the manual safety off, rack the slide, and, without touching the grip safety, pull the trigger and see if anything happens. If not, go to 3.
3. Drop the hammer. Push in the grip safety and hold it in. Then pull the trigger while holding the grip safety. Now, take pressure off the grip safety while still holding the trigger. Does the grip safety stay in? Release the trigger. Does the grip safety pop out?

Report back.

 

[Bountied]

After removing the Series 80 parts and putting in the Series 70 shim I started having the following problem. With the magazine installed, when thumb cocking the hammer it won't catch. Rack the slide and the hammer locks back but won't fire unless I drop the magazine. It appears the grip safety is involved. It appears the grip safety stays depressed unless I drop the magazine. What can cause that? Any ideas?

I think series 70 parts in a series 80 pistol can cause that.

 

[Old Salt]

Well. Tore the pistol down for the third time and reassembled it being extremely careful. It is now working well. Will range test it soon. All I can imagine is that I got the sear spring in improperly. Think I may have had the center spring tab under the sear instead of on top???

 

[John from MD]

Well. Tore the pistol down for the third time and reassembled it being extremely careful. It is now working well. Will range test it soon. All I can imagine is that I got the sear spring in improperly. Think I may have had the center spring tab under the sear instead of on top???

That will do it. The trick to putting the backstrap back together is to capture the sear/trigger spring with the mainspring housing while installing the manual safety.

 

[Magnumite]

Well. Tore the pistol down for the third time and reassembled it being extremely careful. It is now working well. Will range test it soon. All I can imagine is that I got the sear spring in improperly. Think I may have had the center spring tab under the sear instead of on top???

Most likely the left leaf of the sear spring under the sear. Common error. Preventable by:
1. Placing sear spring from well above the lockwork, not sliding it into parallel to
2. slide mainspring housing about 80% of the way up after placing spring;
3. double checking after sliding the mainspring on.

EDIT TO ADD: Make sure the shim is not too thick. Too thick will cause the lockwork to bind.