M*CARBO Brotherhood

Hammer bushing issue in Gen1

Had an issue with the hammer bushing in my gen1 9mm multimag. Would like to see if anyone else had had the same issue. I pulled it all apart to install that, along with an asger trigger, fed ramp, and grip pins. When I put it all back together the trigger wouldn’t reset properly. Nothing audible, and it took two pulls before it would reset. Pulled it apart and reassembled 3 times before I realized it was the hammer bushing causing the problem.

On the stock one, it’s a metal pin with a plastic bushing fixed to it, with a long side of the pin out one side, and a short end on the other. The stainless one from mcarbo appears to be one piece, all steel, with the bushing machines into it.
When I compared the two, the bushing was in a different spot on the shaft. Basically there was more long side, and less short. This apparently caused the hammer to be under pressure from the grip halves, causing it to not move properly. Put it back together with the old bushing and everything works perfectly.

Anyone else have this issue? Anyone else use one of these in their gen1?

For the record, it was mid October when I found this out. I contacted mcarbo, they took a few days to get back to me, then sent a shipping label to return it so they can evaluate the bushing. They received it back a month ago, and I haven’t heard a word since. Not even a confirmation that they received it and are looking at it or anything even though tracking shows they got it. I’m expecting that this is a part, and money, that I just have to consider as flushed down the drain at this point. It does however answer my question about ordering more stuff for other guns from them, but that’s a different discussion.

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That’s a darn shame. I can recall having a similar trigger reset issue on my 1st S2K, that gun I did the entire internal parts kit. The problem I learned was that I didn’t have the Hammer bushing located all the way down when I closed up both halves. Your issue sounds a little different and could be the part measurements are out of tolerance (if so bad on Mcarbo quality control). If you have a pair of calipers or a 5in steel rule measure the part compared to the factory hammer bushing. It won’t take much to throw the internal parts out of alignment when tightening down the plastic outer halves. It is still my belief that the plastic frame of the S2K is the culprit of many internal and alignment issues… Me included
Hammer Bushing

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Don’t give up on M*CARBO - their customer support is good but they’ve had the same problems other businesses have had with the lockdowns and may have just missed this one. Email, call or mail them again and ask what’s up.

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Yeah 00Buck, the overall length was the same on my old and new ones, just more length on the short right side from the Pic and less on the left. This caused it to bind the hammer when reassembled.
Phuzzy42, I did email them again, I’ll keep my fingers crossed, but over a month without any word at all is not exactly great service.

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@jwjeep Did you Watch the Installation Video by Chris, Not trying to be a Smart Ass But I know that somewhere the spec’s are There, for the Total Length,in Regards to the Bushing.
As Far as to M*Carbo getting back to You’ They have Really been a little Busy here Lately With Covid ‘‘B.S’’. And Hurricanes and Other Matters. Contact Chris Nelson Via E Mail He will Respond.

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Pick up the phone and ask for some answers… They’ll provide you some input and confirm they have it… Then, follow up again if needed in a week with another call… Keep a log of everyone you speak to…

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Yes, and the total length is correct, what’s not correct, for my gun at least, is where the bushing is on the shaft. Since the bushing doesn’t move on the pin, it has to be in the correct spot or it doesn’t fit correctly. Interestingly enough, for keltec the bushing and axis pin are two separate pieces, so the bushing can be moved on the shaft. My original didn’t move at all, unless it’s just very tight and I didn’t apply enough force to find out.

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@Jwjeep The Mcarbo S.S. Hammer Bushing is 2 piece affair. It’s pressed onto the pin and should protrude about .175". Take a hammer and wack it to the correct length or use a vise as a press.

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@Jwjeep @Don68 is correct. The MCarbo SS hammer bushing is a two piece pressed fit part. If you don’t have access to an arbor press use small sockets as a punch to move the bushing on the shaft part to mimick the factory bushing measurements. I have almost 20yrs of cnc machining and mechanical engineering background and issues with factory parts like this drive me crazy on no matter what I’m fixing :joy:

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Are you serious? The response I got from the “M*CARBO Lead Gunsmith, R&D Specialist” (copied from his email signature) was that he wanted it back to inspect it and evaluate if it’s a design flaw or a part out of spec. Nothing visually on the one I got indicated that there were two pieces to it. In pics on the web the bushing looks chamfered and pressed onto the pin, on mine it was not, and appeared to be machined out of a single piece. I wonder if they changed the design? You would think the lead technical guy would have a clue about how it’s made. I do own a press, but even easier would have been a small socket in the bench vise. If it is still a 2 pice part then more direction and 30 seconds of work would have corrected a month and a half of frustration and customer dissatisfaction.

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Ok… This crazy! So, I have 3 early produced Gen2 S2K’s, two are stock, one I did the internal parts kit. If I recall (I have a terrible short term memory) it was a two piece pressed SS part. I currently have a fourth S2K build in-progress and am waiting on the full internal parts kit. The Pic I posted was an extra hammer bushing my brother sent me yesterday. I’m wondering if the Hammer bushing has had revisions?! As soon as I get my parts kit in I’ll post a Pic here.

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So, after looking it up, there’s a video from mcarbo about this part. Chris brags about the .175" standoff on the short side and how is machined and fixed length so the bushing doesn’t move like the original could. Maybe the bottom part is pressed in, but the smaller side is a fixed machined part according to the video. It could be that this isn’t the part causing the problem in my gun, but something about it is keeping the hammer and seer from functioning properly. Would be interesting to know if it is fixe or movable, and if that’s really my problem.

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I’ve watched the video on the Hammer bushing install a few times. I’ll have to take Chris’s word on the part itself. Keep us posted on your cure for your hammer bushing issue :metal:

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Just to update everyone, I got an email from them, and then I called and spoke to Jessica just now. They’re sending me out a replacement bushing, but never checked the one I sent back to them. They also did confirm that it is a fixed bushing, and is not able to be pressed to a different position on the shaft.
Basically, they say that it is a problem they’ve seen on Gen1 Subs, and that “pushing harder on it during install” will fix it. I’m doubtful, but we’ll see I guess. When I get it we’ll take a really good look and comparison of the old and new parts, as well as the fitment of everything into the frame halves when reinstalling. Seems dubious that I have to push really hard on the “precision” part to get it to work, and the stock part drops in with no issues at all, but we’ll see.

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@Jwjeep So Far for Myself in Past’ Jessica has Always been '‘Right On’‘To What She Has Suggested’ as Per the Issue.

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Unless you think from the machining perspective… making a “precision” part that fits into a range of 1-15 year old plastic cavities that are most likely oversized due to repeated batterings. I assume its by design that the replacement is oversized to fit more potentially well worn receivers.

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Yeah actually, if you’re going to claim high precision and spend every second talking about the tolerances and fit of the part, I do think it should be actually precise and work in its intended role. Let’s not forget it was the manufacturer who asked for it back so they could check its dimensions and verify it meets spec. The fact of the matter is that the only thing riding on the bushing part of this piece is the coils of the spring, the hammer pivots on the axis shaft, which is stainless from the factory originally. Kel Tec only sells one of these parts for both generations of the gun, there should be no difference from gen1 to gen2, and each one should be the same as the last. If there are differences in your manufacturing process that cause inconsistent parts, they’re not at all precise. If there are allowable deviations in the fit of the weapons they’re going into, then all the precision in the world becomes marketing by. You can’t have both.

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I would bet the fit issues is on the Keltec plastic parts. Cnc machines will cut parts very consistently as long as the operator pays attention to their cutting tools. That’s where the QC dept comes in. Large mass produced manufactures want to use the loosest or biggest tolerances that will function. That makes them cheaper to produce because your scrap rate goes way down and your QC cost is lower as well, cycle times can be faster, etc. I’m sure the MCarbo bushing is made precisely to their prints but that’s not to say the grip halves may be on the edge of their allowable tolerance. Without Keltec’s specs it’s hard to know the exact answer. But that gives you a little insight to the mfg aspect. Unless you are making all the parts for an assembly it’s hard to make everything fit perfectly without having ranges of size parts and putting it together like puzzle.

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I agree and comparable to my comments on this above.

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So, it took weeks to finally get, but they sent me another hammer bushing. Installing went the same as the original one I got from mcarbo, i.e. it didn’t fit or work correctly. Same issue, long side that goes through the hammer was too long. This allowed the hammer to move side to side in its slot and on the seer. After test fitting and measurements and more test fitting… I decided to modify it to make it actually work. Worst that could happen would be I destroy it and it never works. Anyway, I filled down the long side shaft and chamfered the end, so it matched the original in shape and distance to the bushing. This was really easy with a file and a diamond stone. Test fitting seemed fine in function and alignment as the original one fits. Reassembled completely and hand cycled lots, all good. Took it to the range and fired 60 rounds through it and no issues except 1 stovepipe which was probably cheap bulk ammo.

My point isn’t that their manufacturing produces inconsistent parts, that was their guess. My point is that the parts are as designed, but the design is flawed. “We produced our design perfectly” is not the same as we produced a perfect design." If different guns need different positions of the bushing on the shaft, your part needs to accommodate this. Also the there is no such thing as the correct standoff on one side or the other if this is the case. There should be a disclaimer on the part description that it “may require modification in some firearms to function properly” or something to that effect.

Also, just as a word to others for the future who are looking at this part. Your hammer already pivots on a stainless steel pin. The bushing is for the hammer spring to wrap around. When you replace this part, the other side of the hammer spring on the back side of the hammer still wraps around a plastic bushing that’s molded into the other side of the grip. Were I to start again, I wouldn’t bother with this upgrade at all.

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