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s20 underfolder (maybe?)

4K views 12 replies 3 participants last post by  smartbomb 
#1 ·
didnt want to hijack voland s20 thread so started new.

after beating my head against a wall trying to get the gas knob out, i finally get to start something fun. i am deciding whether to go u/f or not. my decision hinges on this. looking at my u/f trunnion compared to the s20 receiver, something looks off. if i line up the upper rivet hole in the trunnion to the upper rivet hole in the receiver there is about 3-5 mm of excess receiver hanging off the back.






my thought was to drill a new hole but it would be very close to the old, almost to the point of an oval. i think it would eventually slip and become loose the other alternative would be to trim the receiver to fit the trunnion but that would also mean trimming the cover.

am i missing something?

well here is the progress so far.



 
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#5 ·
It should work. I would line up the U/F trunnion so that the slot for the recoil spring is in the same location as the factory one. If the holes don't line up, just weld up the old ones and drill new holes.

On my build with the polish trunnion, only the long rivet hole lined up with the factory trunnion. All other rivet holes were off, and I welded them shut and re-drilled.
 
#6 ·
i think thats what i'm going to do. there are no holes that match the romy trunnion. the top set are close but no cigar. i can weld the holes like i did on the side rail and redrill. its only 4 more holes. it took less than 20 minutes to weld and grind the rail holes and the old trigger holes.
 
#11 ·
If it's going to come out (some don't), try a large punch and a couple good smacks with a heavy hammer from the side, if it doesn't move in two or three hits, it most likely won't.

Yeah I need it for an S12, I got one of the first Chaos extended rails and mounted it to the rear of that (had to thin it down to fit rail groove) with a bead up front, well the first gen long rails weren't made right and you couldn't field strip it with it on. So that was a waste of money & time. :(
 
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