M*CARBO Brotherhood

Sear & Hammer Bushing

Did some internal upgrades, including a new trigger bar. On reassembly, when the sear is fully seated, the trigger bar window slips off the sear pillar. If I slide the sear up a little, the pillar stays in the window. Everything’s supposed to be fully seated, so I’m puzzled as to what’s going on…has anyone else had this experience? I uploaded two pics, but one is showing as a link for some reason.20210312_224757|375x500

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Is everything seated correctly, including the receiver tube? Is the hammer bushing seated all the way? What is holding the trigger bar up - it has to be riding on something else instead of the sear like it’s supposed to.

Have you watched Chris’s video and checked your work against his? It’s usually something simple and you have a “Doh!” moment.

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I’ll second that something that isn’t seated fully.

Yes sir, I’ve watched Chris’ video, pausing & rewinding a bunch. Also read quite a few posts here. I’ve pushed everything down, and everything’s properly seated, but the trigger arm & sear post keep separating at the slightest movement…

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As far as I can tell, everything’s properly seated…

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Does it look like this if your looking straight down on it? I can’t tell from the angle of your pics, all I can tell is that something doesn’t look right.

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Yes, mine looks like that, except the hammer is in the cocked position in the pics I posted. I installed the steel hammer bushing, and it seemed like the trigger arm was at a higher level while resting on the bushing, as opposed to its position on the trigger. I pulled the old bushing out and compared the two, the new bushing looks slightly longer than the old one. Maybe that’s the problem? Out & about right now, but I’ll take pics & post when I get home.

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First of all drop the hammer - it puts a lot of tension on everything when it’s cocked, especially since only one side of all the pieces in there is supported without the right-side grip half. Second, I’ve found that locking the barrel all the way open really helps get everything lined up and takes more tension off things. The bolt must not be inserted, the receiver tube must be seated all the way, the hammer and sear springs must be located properly, the trigger bar must be sitting in the cutout in the receiver tube - just like the picture above.

Other questions - have you compared the old and new hammer bushings? Any differences in sizes? If you put the old hammer bushing in, does the trigger bar do the same thing? The hammer and sear springs look okay in your pics. In the second one, the trigger bar looks like it’s sitting on the hammer bushing but above the sear post. The hammer bushing looks way too tall but it’s hard to tell with this pic.

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The new bushing is indeed slightly taller than the old one. I’ve disassembled the trigger & hammer groups, and am re-installing it all now. We’ll see how it goes…20210313_210404|375x500

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Hopefully it all goes well. Initially i had a hard time getting the trigger bar to stay down as I was assembling it, I don’t remember how I got it, but it finally stayed down. Now that darn sear spring, heard it just reentered the atmosphere yesterday lol.

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Well, guess what? I finally got it all to fit, and I was able to close the handgrips. Just gotta install the new rear notch sight, and we should be good. Last thing I’ll have to do is track down that Magpul sling on the interwebs.
Wonder if NASA picked your spring up on radar? :grinning_face_with_smiling_eyes:

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Did you put it back together with the new parts or did you have to go back to the original ones?

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I finally used the new parts. I say finally, because I’d order something, then a week later I’d see something else…order it…couple days later…“Oh, I gotta have that!”…repeat, so on & so on :grinning_face_with_smiling_eyes:

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Lol. My sear spring launched itself through my fingers into the next room. I found it 2 days later. Glad there was a replacement in the MCARBO set. Man there’s a lot of tension on that spring. You’re right about pushing everything down and in place and having the hammer uncocked.

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@Patrick welcome to the brotherhood, awesome place here. Your lucky it was the stock sear spring. I still haven’t found the mcarbo spring lol.

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Thanks. Appreciate the welcome. I love all the ideas and great suggestions here. Good luck finding that spring.

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