Hello, I have a 1991A1 ORM. I installed a knurled/checkered war-era hammer of unknown make/origin, not wide spur. The first "notch" on the front of the hammer has short hooks instead of the 90 degree "shelf" as on the 80 series hammer. Now, it all worked fine until I put in a magazine. After that the gun would seem to be stuck in a safety on position. Pop out the mag and rack the slide, it is fine again. Put the 80 series hammer back in, and it's fine again. Any ideas on which part of the hammer is causing the problem? Any input appreciated.