I just received the wolf captive spring upgrade to replace the weak trigger return spring in my m9a1 and inox compact. I knew that this part was incompatable with the polymer trigger in my guns, nothing a drill press can't fix... The back of the A1 poly trigger is much higher than a steel non poly trigger. In order to create enough clearence I need to remove about 1/8 inch diameter material for clearence of the spring guide. Well my first attempt failed. These triggers are so hard I broke the first 1/8 bit and choked up on the second one to reduce chatter and hanging on the press handle I couldn't get it to bite. These things are harder than rocks. The steel isn't even scratched. To drill this trigger you would need a better press and bits than you can get at sears. My craftsmen press is normally enough to drill anything I need. Anyone that is ditching these poly triggers because they think they are weak is an idiot. The steel under the coating is stupid hard, I doubt superman could snap one. Round two will be tomorrow with ye olde dremmel and a pack of cutoff wheels and polishing stones and cold blue.