I am putting together my first lower and have a question/problem. I am installing a DPMS mil spec tube on my lower but the castle nut will not start. I can start just a few threads and then nothing. I don’t want to force anything, I did try a little grease, but no good. Should I just get another nut or am I missing something stupid?
Chances are the DPMS tube is out of spec. What is the lower?
The lower is a Spikes. The tube threads properly into the lower. The nut is an Advanced Technology.
Is the castle nut stopping or spinning? If it’s spinning they may have sent you a commercial castle nut with a mil-spec extension, and if it’s stopping it could be the opposite. As said before, it could also just be out of spec. Do some searching here to find the measurements of mil vs. commercial. That would be a good start to figuring out what you are dealing with.
@ dunderway - the threads/tube diameter/pitch/ etc. Are the same on commercial and milspec extensions. If they weren’t, that would mean there would be two different types of lower receiver.
That’s what I’ve read in my searching. The nut must be out of spec because the tube threads properly to the receiver. I’ll pick up a different nut, thanks.
And the threads look good on the tube and nut? If so and it stops and isn’t going on crossthreaded you might just need to put a little more oomph into it.
That is correct, and embarassingly obvious. Ignore my post OP.
I would try it on a different lower if possible…could be your lower…
Absolutely not the lower. There is no problem threading the tube into the lower. All problems are with the tube and the nut. I’m gonna place an order for some more parts tomorrow, I’m going to get a different nut.
This is what happens when you buy questionable shitty parts. DPMS tube+ ATI castle nut= FAIL.