Just finished my build and the sear pin hole is slightly to big the pin fits in just a little to easily and comes loose once in a while, any suggestions on fixing this?
Try Brownells, they have oversized pin sets. I use these pins near anytime a trigger job is called for. GI parts kits are pretty loose tolerances.
Are you installing the pin from the left side?
The thumb safety keeps the sear and hammer pin in place.