1911 Locking Up. Insight?

[Southern Raider]

I have a Colt Officers 1911, series 80 that I obtained in trade. After polishing some internal parts, I noticed that when firing it would sometimes lock up. (Hammer cocked with me pulling on the trigger, but nothing happening.) By disassembling the gun, I could reset the mechanism.

Upon inspecting another series 80 1911 I had worked by a well known gunsmith, I noticed that the right front edge of the sear had been heavily filed/stoned along its length to remove material, and now it dawned on me why. The series 80 parts create a step on the right side of the sear, which the sear could hit if things weren't perfect. Sure enough, I noticed that my Officer sear could slide over enough to hit this ledge and be stuck.

Is this a widely understood possible issue for series 80 1911s? I have tried to duplicate the beveling of the sear, which has improved the situation greatly, but it will still catch occasionally. At least now I can reset the trigger by cycling the slide.

Any reason why I wouldn't remove that ledge internal to the frame? Any other fixes to this problem?

 

[RogersPrecision]

Colt built quite a few pistols with that ridge to the right of the sear. I've seen numerous factory fresh guns where Colt heavily beveled the right hand, upper, forward edge of the sear to clear the corner of that ridge. More recent examples are now properly machined and that problem is over.
I don't think I've ever seen one where the ridge would actually stop movement of the sear.
I assume the stock firing pin safety levers are both in place? Or a proper thickness shim?
Without the levers or shim, the sear would be free to migrate to the right and then run into the ridge.
I guess this could also happen with some odd example of tolerance stacking. Thin levers, wide cut in the frame, wider than usual ridge etc.
I hope this helps!

 

[Southern Raider]

Chuck,
Thanks for the insight, it is pretty much spot on with my observations. The firing pin safety levers are indeed in place. I usually run a stone across the sides of these to knock off burrs as well as the sear sides, and it appears as though this dimensionally changed things enough to cause the problem. I believe the sear is aftermarket, further aggravating the tolerance stack up.

I can simulate the problem with the slide and grip safety removed. Using a tool to push the sear to the far right while pulling the trigger, the sear does catch.

I can certainly bevel the sear further, but the tip is catching. More bevel will decrease the engagement surface with the hammer. Do you think this would be OK?

 

[RogersPrecision]

I radius that edge pretty heavily. Heaviest at the pin hole and decreasing up to the sear nose without losing any engagement area.
Try it, test it as you mention above.