Got an email from mcarbo saying that I’m not active enough. I don’t like to talk unless I have something to say,so I’ll give it a shot.
There is a fairly simple way to eliminate trigger creep by removing material from the radiused surface adjacent to the sear contact surface on the hammer of the sub2k. This is a .250" radius and is concentric to the hammer pivot hole(they share the same center point). This is because the surface to be ground and the sear face have a similar relationship to that of a camshaft lobe and lifter on an engine, as was evident by the wear on the face of my sear. In my opinion, if it is ground flat, it will accelerate wear on the sharp edge of the sear. You don’t want this because eventualy it will cause inconsistant trigger break and probably, after a while, hammer drop or maybe even full auto. This is only my opinion, you can take it for what it’s worth.
I should first mention that I am a retired machinst with forty years in the trade, and I did this work on one of my milling machines. Please don’t roll your eyes in dispair just yet. This can be done on a drill press of reasonable quality, but requires a little different set up and is not as easy. Also, there is guy with a website called the ktgunsmith.com. He knows what cooks on this subject, but uses expensive jigs and fixtures that I can’t justify dropping the bucks for. Read his article on sub2k trigger creep before reading my stuff below so it doesn’t sound like a bunch of complicated happy crap.
What I did was face flat a 2"x2"x1/2" piece of aluminum and drilled and reamed a .125" diameter hole about 1/8" away from the edge, cranked the mill table to the left a couple of inches and pushed in a 1/8 dowell pin(you could use the kel-tek hammer pin or probably even a 1/8 roll pin). I then slipped the hammer onto the pin, took a short piece of 1/8" rubber hose and pushed it over the pin down against the hammer so that the hammer could rotate back and forth on the pin but not move up and down. Then, I put a 3/8" diameter fine grit dremel wheel in the spindle, cranked the table over about an inch away from the wheel and brought the wheel down so the bottom of the wheel was just below the bottom of the hammer suface. I then carefully cranked the table over until the wheel just barely touched the hammer surface to the wheel. Then I rotated the hammer back and forth on the pin until there was no grinding sound. I cranked the table over .001" and repeated the same process until I had removed .030" from the hammer surface, removing and checking progress frequently. I have a
tubing micrometer to check this, but calipers will work just fine. On my hammer I ended
up with .157" from the edge of the hole to the surface that I had ground. I then cleaned
it, lubed it and assembled the sub2k. I almost greased my shorts! The creep is so minimal,
that I had to close my eyes and slowly squeeze to even feel it. The pull weight on my
lyman pull gage said 4lbs.8oz. So I took the sub apart, flitzed every thing trigger,
including the face of the sear and the surface I had just ground, including the sear contact points on both the hammer and the sear, reassembled and now have a pull weight of 4lbs.2oz.
and a “glass rod” break, right at the wall.
If anyone is interested in doing this on a drill press I can post my idea for a simple jig
you can make. Also, depending on any interest, next week when my mill is freed up from my
present project, I can post a picture of the set-up I used. I’m only posting this now be-cause of the email I got from mcarbo.
All said and done, this mod, along with all the great stuff from mcarbo, the change from what it was to what it is, is more than I ever imagined.