![]() ![]() Hence don't think that the problem is the channel in the upper rear lug, but something like the rear lower lug just a hint too long, and the reason that you can get the upper to go any lower to close up the gap isntead. If the upper binding out on the top/back of the lower ring, or is the lower lug just a touch too wide, or bottom of lug too long, and that the reason that you can get the lower to upper gap to go away. Seeing the needed amount of alignment of the lug channel needing to go down, as I see the gap between the upper and lower as well. Production tolerances aren't what we all think they are - it's not about tight tolerances at all, it's about tolerance stacks. I borrowed my little brothers wooden mallet for beating pins thru round holes (Fisher Price) and voila, made them fit. We might say that assembling these is a lot like Legos, funny, I remember some of those not fitting well together either. ![]() But the alternative is either filing out the holes, or using a known smaller pin, and good luck ordering one. If there is any risk, then, don't hammer. We have one of each and deal with it the best way we can. Of course, they get thousands of parts to mix and match and it's a tedious exercise of matching the best fits. This is not slipshod manufacturing on the part of anybody, it's just part and parcel of the normal issues makers have to fix and they hassle with it all day long. That is what you pay for when you buy a complete rifle.īuy it like we did, parts here, parts there, now YOU THE BUILDER get to deal with it. On an assembly line, tho, QC has already found which batches work better with each other, if not already addressing it by massaging one or the other before anodizing. Both makers will tell you - and you could probably prove it, too - they built them milspec. Now, since you won't do that - and we know the pins will go in individually - what we have is the difference between the upper center to center dimension and lower being at the opposites of the +/. Had the same issue, took a small dead blow hammer to it, runs just fine and it's loosened up enough I can get them apart with finger pressure. In the meantime, has anyone run into this? So close to finished and yet I find myself with another obstacle to overcome here. Micrometer should be arriving in two days to get a more accurate idea of what maybe be going on. I'm not sure if the tiny ridge at the base of the upper rear lug is the reason for the misalignment (shown in picture 1). Aero upper on JP Enterprises lower though. ![]() Then took the DDM4v7 upper and put it on the JP Enterprises Lower and that too fit like a glove. I'm not getting any interference from the receiver extension either.įor what it's worth, I put the Aero upper on a DDM4v7 lower and both takedown/pivot pins went through without a hitch. Putting the takedown pin in on the correct side, it barely gets in and doesn't budge shortly thereafter. I can almost get it through from the opposite side (I get through to the point where it gets through first 2 holes, but hits a wall and cant get through the 3rd hole (right side takedown pin hole). I tried aligning the two with and without the buffer in, with and without the BCG/CH in, etc. Tried to provide all relevant angles with lighting to show where fouled up contact points might be, where the holes are misaligning, etc. Front pivot pin lines up just fine, but rear takedown pin holes are not mating properly between the upper and lower.įor what its worth, the upper is Aero Precision ( Upper) and the lower is JP Enterprises ( Lower)īelow are pictures of the issue I'm running into. Building my first pistol AR and all has gone pretty well until I was getting ready to mate the upper and lower. ![]()
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