In this post, we are going to talk about trigger pull. Mine is terrible. It's hard and the best way to describe how it feels is to compare it to a rusty ratchet wrench. It starts hard, clicks and scrapes as you pull and finally, just barely before it goes off, it smooths out. You can actually hear it scraping and clicking in there. So I decided to do something about it...or at least TRY to do something about it. I had a feeling that the problem was the sear so, I cocked the action, took the trigger housing off and used a screwdriver to push on the sear where the sear trip in the trigger group fits. Sure enough, I could feel the scraping and clicking. Time to take the sear out. It's held in the receiver by the bright shiny pin seen here below the charging handle slot:
I just placed a punch on the pin and it pressed out using only hand pressure. There is a spring in there holding the sear under considerable pressure so parts went flying up into the receiver when I removed the punch. I'll figure out how to get it back together later! After fishing the parts out of the receiver I took a picture of them:
Forward is to the right and we are looking at the right side and bottom of the sear. The top of the sear spring fits into the bottom back hole and there is another hole in the receiver for the bottom of the spring. This spring is of a larger circumference where it fits into the sear, presumably to aid in assembly. The step on the bottom towards the front is where the sear trip on the trigger engages. Also pictured is the retaining pin which obviously goes through the hole in the center of the sear.
Here's the scalloped area on the front of the sear where the disconnector goes:
Here's a better look at the bottom of the sear:
And the top of it:
The rear surface of the sear is what engages the bolt carrier notch and as soon as I looked at it I saw why the trigger is so scratchy. It is shown here in two pictures:
All those lines going across the polished surface are the cause of all my trigger problems. As the trigger is pulled, they scrape and stutter across the mating surface on the bolt carrier until they are no longer touching it and the pull evens out just before releasing the carrier to fly home. So I broke out the emery cloth and my diamond encrusted sharpening stone and went to work, being carful to keep the surface straight and flat and only removing exactly enough metal to eliminate the marks. I was also careful to stay away from the very top edge of the surface for fear of making the rifle unsafe when cocked. Additionally, I left just a little bit of the bottom groove to see if I could feel it when I pulled the trigger. If I could still feel this groove after reassembly, it would also tell me just how far down the sear face the carrier notch grabs. Here are two pictures of what it looks like after polishing:
The fact that I stayed away from the top of the surface and the partial notch I left are clearly visible. The ease with which I removed the marks does have me a bit worried though. Perhaps this surface is not hardened? If not, were those grooves made by SMG or are they an artifact of the bolt carrier striking the sear in the forward stroke? If they are from the latter, they are going to show up again with use and the trigger will again become funky. You can't keep dressing the surface or you will eventually run out of sear! I'll keep an eye on it and report back.
Reassembly was an absolute pain in the arse and I can't exactly describe how I did it because it took a lot of fidgeting. There is a technique to it though and I'm sure that it would go easier next time. Once it was back in, I put the trigger housing on and quickly found out that it wasn't in right so I had to take the sear back out and start over. The second time worked and back together the rifle went.
The result of my efforts is a MUCH smoother and lighter trigger pull. I can indeed feel the notch I left on the sear face so I know that the sear and carrier have a good engagement but the drag is minimal and only felt at the very beginning of the pull. After that, while it's still quite a long pull, it's silky smooth all the way to let off. As stated, the weight of the pull is significantly reduced too but I unfortunately do not have a tool to test that.
Of course, a range test tell me a lot and use will tell me if the marks will return. So, should YOU do this to your rifle if you aren't happy with the trigger? Only YOU can answer that for yourself. But I will say this......unless you know EXACTLY what you are doing, don't mess with it. The absolute last thing you want is an unsafe rifle. So if you have any doubts whatsoever about your abilities, contact SMG and ask them if they can polish your sear. Of course, you may be perfectly happy with your trigger already because it's as smooth as glass. If so, you can just disregard this post because you don't need it!!