Just finished a precision recce build on a Sun Devil Billet lower and Vltor MUR billet upper. The rear takedown pin is really tight. When the upper and lower are mated, it requires a brass punch and small hammer to get the pin out. Is this going to be an issue? I would not want to egg out the rear takedown pin holes or anything. I was hoping for a good solid fit between the lower and upper, but this may be too much of a good thing.
Also, after installing the barrel, I noticed that the bottom of the bolt up plate for the DD Lite rail I installed was coming into contact with the bottom of the receiver block. While torquing up the barrel nut it was actully crushing the lower part of the bolt up plate into the delrin receiver block. This would have applied some uneven force as the barrel nut was being torqued down (to 65 ft/lbs). I don’t expect it was much, as the delrin gave some and the bolt up plate left an impression in the block. Again, does anyone think this is cause for any concern?
Probably worried about nothing, but am curious to hear from those with more experience on these issues. Thanks.
I had to remove some of the plastic from my DPMS upper receiver blocks for Lite Rails and a few others. Try to see where it’s binding before doing anything. I’ve had good luck with fitting Sun Devil lowers on VLTOR and Larue uppers. You may need to either loosen or remove the set screw in the back of the Sun Devil lower.
Thanks for the response, gotm4. I forgot to mention that I bottomed out the set screw in the back of the Sun Sevil receiver, to make sure that was not the issue. At this point, everything is together, and unless someone thinks that the barrel needs to be taken down and retorqued, that is probably the way it will stay, at least until I get a chance to shoot it. The tight fitting upper and lower I expect will wear in somewhat with time, but right now it fits almost too snug. I am not sure how much of an issue this really is.
I guess for now, unless someone can tell me that it is a bad idea, I will go ahead and leave things as they are, shoot it, and she how it does. Any further input will be much appreciated.
Cool. I don’t think you should have any problem with the barrel unless you bent the backing plate. The upper/lower fit will loosen over time, you can help it along sometimes.
I needed a punch to get the pin out of my Noveske lower/MUR upper until I traded the lower to someone who had the next number. My current Nov lower is much older and the fit isn’t so tight.
I don’t think I bent the backing plate, but I did notice this morning that the barrel is not centered in the DD lite rail. The barrel is slightly closer to the port/left side of the end of the rail, not much, but just enough to be noticeable. I bridged a carry handle over the receiver and handguard when I was tightening down the screws between the backplate and handguard to try to keep things true. I’m not sure if the barrel or the handguard is what is off center.
Again, I am not sure if this indicates a problem, and if so, what Ishould do about it. Sorry to keep coming back with all these issues, and I greatly appreciate people taking time to respond.