After reviewing this, I notice a little lack of detail. Perhaps I can be of assistance in your continuing education.
First off...when you test the thumb and grip safeties, you'll want to make sure that the sear isn't moving when the trigger is pulled.
Engage thumb safety and pull the trigger with about double the normal force needed to fire the gun. Place the safety in the FIRE position. Hold the left side of the gun to your ear and gingerly pull the hammer just a tiny bit past full cock, being careful not to let it hit the grip safety tang. Listen for a light click. If you hear that, it's the sear resetting after the hammer is lifted off of it. Not good, especially if the hammer hooks have been shortened and squared in a typical trigger job...and the sear has had a breakaway/escape angle cut onto it. You don't want any sear movement in a pistol like that. Not so critical with true-to-Browning's specs...which has long undersquare hammer hooks which captures the sear and tends to pull it back into the hammer. GI Ordnance spec allows for .005 inch of sear movement. Tuned trigger/fire control groups do not.
Same "click" test for the grip safety.
Disconnector test. The test is to determine whether the disconnect is in fact disconnecting and allowing sear reset when the slide cams it down into the frame.
First...The disconnect isn't a safety. Keeping the pistol from firing out of battery isn't its function. Unless there's a serious issue with the upper lugs' vertical engagement, the gun won't fire far enough out of battery to blow up anyway. It's mechanically impossible.
When the slide is about .100 inch out of battery, the upper lugs are still vertically engaged with those in the slide. If the gun could fire...which it can't...the slide and barrel can't separate and allow the breech to open. Push the slide .075-.085 inch out of battery and observe the relationship between the hammer face and the butt of the firing pin. At that distance out, the hammer is caught by the bottom of the firing pin stop, and can't reach the firing pin.
Second...In conducting the disconnect function test, the slide should be pulled 1/16th inch out of battery...not a quarter-inch. At that distance out, the hammer is pushed off the sear, held by the bottom of the center rail, and it can't fall no matter what the disconnect does or doesn't do.
