I'd like to revisit the slot that the two pins ride in. This seems to be the most important spot, but I didn't have a way to get inside it other than to cut the sandpaper into thin strips, thread a strip thru the slot, and then run it back and forth. Anyone with a better idea?
The trigger pull weight of a gun, particularly a double-action (I'm not going to get into the debate about "it's not double action because it doesn't have a hammer"), is dependent on two things: friction and springs.
The design of the gun generally assumes that friction will go to near zero with use and then the springs will be the main factor. You can either put one or two thousand rounds through it, or you can mimic what that does and enjoy good shooting right away.
The SW40VE is well-designed, but rather cheaply manufactured, which means the out of the box heavy trigger-pull is mostly caused by friction, and I think that posters who are happy with the trigger out of the box probably got a smoother specimen than I did.
I've looked at the internet videos and seen that they mostly involve doing something with the springs. If the main problem is friction, then messing with the springs is breaking something that isn't broken, instead of fixing what is broken. I've got guns that are over 100 years old and still in good working condition, ball-point pen springs are not built to last 100 years in a gun.
The problem is not in the trigger but in the lower sear mechanism. The "gritty" feeling comes from there, as does a lot of the friction.
The sear in any gun is two metal surfaces like blocks that face each other under spring pressure when the gun is cocked and the trigger causes them to slide apart, abruptly releasing the hammer, or in this case, the striker. Technically the sear is the single part that holds back the hammer (or, in the Sigma, the striker tang) but I'm using "upper" and "lower" here for clarity.
In the SW40VE the lower sear and sear housing are located in the rear of the frame. The lower sear is a cam which, when connected to the trigger by a simple metal link, will move rearward and downward, thus cocking the striker and then releasing it through a single trigger pull. The upper sear, or striker tang, is in the slide, connected to the striker.
The "grittiness" is caused by the fact that slot in the lower sear has been roughly machined, causing the bar that pushes the lower sear rearward to "chatter" through the machining marks. Also, the lower sear has an "S" shaped curve at the rear which interacts with a plastic ramp in the sear housing to drive the cam downward as it proceeds rearward. Again, rough machining marks here cause friction. The plastic is not the smoothest it could be, due to mold marks.
Finally, the surfaces of both the upper sear (attached to the striker in the slide) and the lower sear are roughly machined surfaces, causing friction.
So the real "trigger fix" is:
1. Smooth and polish the contact surface of the slot inside of the cam that is the lower sear (one poster said he took most of the fuzz off a Q-tip and put it in a dremel chuck, using metal polish to polish the slot at a very low speed.)
2. Smooth and polish the part of the lower sear cam that contacts the plastic sear housing as it moves rearward
3. Smooth and polish the mold marks on the plastic sear housing that contact the sear cam
4. Smooth and polish the contact surface (which contacts the upper sear) of the lower sear
5. Smooth and polish the contact surface of the upper sear (which contacts the lower sear) (you need to remove the striker from the slide to do this)
Some purists will object to 4 and 5, saying that the sear will be rounded and less crisp. But if you carefully polish the surfaces with the flat stick, that will be minimal. And a crisp sear is much more important and noticable in a single action than a double action.
WARNING: Do not use a power tool for these steps! It is too easy to remove too much metal.
I used a flat metal fingernail file from Revlon to get the machine marks out (thanks to my wife who gave it to me a long while back). It fits in the slot. I would say that the rough side is about 400 grit and the smooth is about 500.
Then I used a 600 grit "Angle Cut Sanding Stick" (works better when wet) from
www.stevenshobby.com to polish the surfaces mentioned.
You need a jeweler's loupe or some other 10X magnifier to look at the original condition and to see when you have polished enough.
Finally, I lubed all contact surfaces (including the side of the sear housing that contacts the sear) with a Hob-E-Lube dry graphite and molybdenum (HL651). Look for a hobby store that sells electric trains, for this stuff. I like dry lubes or Rem-oil in guns because neither tend to collect grit.
I would say the trigger pull is now smooth and comparable to a Glock 23 or the new S&W SD (which has a redesigned rotating sear mechanism that has its own issues.) Not as good as a S&W M&P.45, which I have also fired. The trigger pull weight breaks at 8 lbs.
