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I have a Top Notch grease mag conversion kit with the lower and the folding stock. I would like to mount a UMP lower instead of the grease mag conversion lower. I was wondering if the UMP lowers would attach thru the pin hole on the Top notch stock.




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Not without modification to the lower.
 

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The folding stock will work but you will need a HDPS block and there are reports of the screws that hold the upper to the TN stock assembly will, especially firing with the stock folded, give way. This is why HDPS went to the single steel rod that goes through one side to the other to hold the upper on. Other wise you can't make the TN assembly fit an HK lower without cutting the lower to accept the TN endpiece it is then forever altered and according to HDPS, ruined. That is their opinion however.
 

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I'm not sure I agree about the screw, but I am sure that cutting the UMP lower for a TN stock block will forever make it incompatible with a HPDS stock block. You cut the rear of the lower off for the TN setup. That missing part is what the HPDS block attaches to.
 

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they will work together 57 ive seen it before. what you would have to do is on the ump lower behind the pin hole where it tapers off you will have to cut/grind some of that off. work from the back forward untill the pin holes on the lower and stock block meet dont go to far or the lower will be unusable. and you'll have get the pin that holds the two together. i cant say anything about the integrity of the plastic block ive heard that the screws will turn in on themseves but ive never seen it first hand. maybe search the forum to see if it acually ever happend or if its just a myth. maybe what you can do since you have to mod the lower is buy the eyelet bolt that goes all the way through from hdps i think there like 25$ get a drill bit the same size and drill all the way through the plastic block that might hold up to stock folded fire better. but think real hard about how you want to do this because like dwill said i dont think you can use the hdps block after you cut the lower.
 

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On my conversion I have the TN stock block/stock. It will not fit a UMP lower without modification. On a UMP lower that back piece that sticks up is actually cut off and a new hole is drilled in the back of the UMP lower to fit the TN stock blocks pin hole. That's how TN does theirs.
 

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oh you have to drill a new hole i thought you used the existing one but i new the end had to be cut how long have you had it like that aluweshus everyone says the bolts strip from shooting with the stock folded is this true
 

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I have a TN converted UMP and haven't had a problem, but then I don't shoot with the stock folded because that's a silly waste of ammo. I hadn't heard of the bolts stripping. What I had heard is the threaded aluminum tube inside the polymer stock block comes loose and free spins when the stock bolts are turned, preventing you from unscrewing the bolts and removing the stock, but I haven't run into that. If that is true, I don't see how in makes a difference whether the stock is folded or not. If the internal tube comes loose from the surrounding material, it's probably likely to do it because you overtightened the stock bolts, or from the general shock of firing, stock folded or not.

I's also like to hear from someone with a TN UMP setup who actually had it happen to them. So far, the only place I've heard it is on a website of a competitor who sells a competing stock block. I appreciate that it's possible, but I'd like to hear it first hand.
 

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. If that is true, I don't see how in makes a difference whether the stock is folded or not. If the internal tube comes loose from the surrounding material, it's probably likely to do it because you overtightened the stock bolts, or from the general shock of firing, stock folded or not.

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I also have'nt seen any examples of this but I think the theory whether tested or not is implying that the bolt in recoil at it's most rearward travel is exerting its energy on the screw mounts with the stock folded and it indeed does because that is all that is holding the upper to the lower here. The energy transfer in this area is pretty indisputable but that changes when the stock is against the shoulder pushing against the force exerted in the opposite direction by the bolt and that minimizes the lateral stress inflicted on the screw mounts. I think this is what he is getting at and this sequence is eliminated with the aluminium block and full length steel rod.
 
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