M*CARBO Brotherhood

S2k Gen 2 Loose When Unfolded

if you didnt have play before the install, it has to be a assembly issue.lets start with the first step. when you you reassembled did you ensure you locked the long leg in the trigger guard?

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I’ll check mine and my buddies today, as we are doing the upgrades on his SUB this morning after we meet for breakfast.

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It’s been many many months since I did the MCARBO upgrades but I am 99.999% sure it had the play before I did anything to the firearm. I recall thinking the new parts (specifically the trigger guard) might eliminate it and the “slop” was due to some of the polymer parts. To be clear, when I talk about movement, I’m not saying it opens up like 1/8", it is minimal but there is movement that can be felt as well as seen. My concern was both for accuracy and safety.

Yes to the trigger guard spring. If I have a chance later I will open it up to verify this but, as this was a new gun to me at the time, I was very careful in watching the MCARBO videos when installing the upgrades (a very handy resource, I might add).

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So I checked my SUB this morning against my buddies SUB (I have done the upgrades on mine, his had been upgraded) and there was no difference between the two. A minimal amount of movement (maybe 1/2 a millimeter, if that) and after completing the upgrades on his there was no change in the looseness. He was amazed that I was able to take it apart in such a quick amount of time and (with aid of Chris Nelson’s video via YouTube) have it back together and functioning in just over an hour and a half.

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@chilipepper does it change brother after the cold bore shot. in otherwords does it tighten up as the gun warms up.

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This is a very good question and one that I cannot honestly answer as I have yet to shoot this particular Subby (as well as the Ruger PCC I snagged more recently). :frowning_face:

I currently live in the “great” state of Maryland and, unlike my home state of Pennsylvania, things seem to be quite different down here when it comes to firearms. Finding a place to shoot has proven difficult. I’ve only managed to find one public range thus far, most places seem to be private clubs with long waiting lists and hefty member fees. Shortly after finding this public range, which was about 45 minutes away, I moved over a toll bridge and an hour and a half farther away from it. Apparently the place is very popular and, as a result, typically very packed. So essentially I have some firearms and now have nowhere to shoot them unless I want to blow the better part of 5 hours getting to the range and back, all with the hope of not having to wait a few hours just to shoot once I get there.

In PA we had public rifle and pistol ranges at or very near many of the state gamelands where I grew up, open sunrise to sunset, no fees, access was easy and you almost never had to wait. In Maryland, I almost get the feeling they don’t want me to shoot my guns…

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So I’ve recently noticed this same issue…when opened & locked, if I apply upward force on the barrel…as if I were attempting to fold the rifle. I’d estimate 1/16 of an inch of play. Never noticed it before. Was reading thru the Brotherhood’s discussion of the issue, so I’ve removed the handguard to inspect. Everything tight as your previously mentioned bull’s butt. Haven’t taken it to the range as honestly I’m kinda worried. Seems to me you don’t want any kind of wobble or slack in that area. So I’m gonna call KT tomorrow & send it in, probably.

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Exactly where I’m coming from @TommyTwoGuns . Just don’t do what I did and #@$! up your barrel spanner nut.

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@chilipepper @TommyTwoGuns my gen 1 has no play, even after over 2000 rounds thru it, the gen 2 i picked up in a swap, cold, i have about .015 cold that goes away after its fired, but keep in mind it doesnt have more than 100 rounds thru it. 0.0625 seems a lil excessive to me, and if its not there for heat expansion ( rifle heats up, cant unlock till it cools scenario) its almost got to be a headspace issue. how many rounds ya’ll got thru em, and do you have a go/no go gauge for 9mm?

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Too late! But I gave up before I did any real damage. Don’t trust my limited gunsmithing skills. I figure they’ll set that right for me as well. This is the first real problem I’ve encountered w/my Sub. Time to see if the vaunted KT customer service is all I’ve heard it is. I’m confident they’ll take care of me.

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I used a hair drier to heat the nut and a little force with the MCARBO armorer’s wrench and it came right off. Also placed a damp cloth on the grip and receiver to prevent over heating the polymer.

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@Shadow7059 That might work, except for I don’t own a hair dryer…:slightly_frowning_face:

At first I thought the MCARBO armorers wrench would work but upon closer examination it didn’t look to be the correct size…plus I’d have to pull off the front site to get it on the barrel.

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Sorry, your right. The armorer’s wrench will not work.

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I have a 9mm sub2k with the same issue.

I also have a .40cal sub 2k and it is nice and tight. After installing the M*CARBO trigger guard it was even tighter requiring a bit more “intent” to snap it locked when opening (unfolding) the rifle. No issues unlocking the barrel and folding.

On the 9mm, the lockup was loose from the factory (as well as a number of other issues like a canted front sight.) Even after the M*CARBO trigger guard replacement, it was still loose and just did not feel positive or correct. I ended up removing the foreend and tightening the barrel lock nut just a small amount (part #103 on http://s3.amazonaws.com/build-keltec/wp-content/uploads/2018/11/sub2000_series_manual.pdf)

You are not supposed to use a tool on this locknut, but rather heat up and hand tighten only. But mine was really locked on and I could not move it in either direction by hand. I ended up using a rubber belt strap wrench and tightened the nut with the barrel in the open and locked position and I tested the lockup repeatedly with about every 10 degrees of rotation to make sure I was not over-tightening. In total probably only a quarter of a turn and now it feels just like my .40 cal very tight and a positive lockup.

Now, I have not been to the range to test it yet, so I’m not sure if any heat expansion will cause issues with the lockup.

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Yep, #103, that’s the one. I say I screwed mine up, I did chip a flute off it but it might still be serviceable. I had to step away from it for a while to cool off. I’m anxious to shoot it so might have another look at it this weekend. I have a mini butane torch, might try that to heat it a bit but don’t want to f/u the plastic.

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Don’t beat yourself up too much … .you can always order a replacement :slight_smile: Assuming you can get it off!

I just ordered the heavy weight bolt to see if it makes much difference:

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I used a strap wrench to get some movement without damaging the nut. It was still very tight and difficult to turn even with the strap wrench.

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Had not noticed this on mine. Glad you posted. Just took mine apart and it was loose. It spun freely by hand . The washers were getting out alignment. Meaning the last square one was canted. I am going dig around in garage as I think I have a strap wrench. Of not I can rig something up to get it snug. I am also going to use that rock set as well

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I found better or easier to take gun apart and just have barrel to work with.

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Workers like a charm. Tightened everything up. Sweet!!!

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