Hello.  

I am building a Anderson lower with a PSA kit and noticed the buffer tube is slightly tilted upward with or without the stock installed.   I put s stag upper on it and can cycle it without any issues.   I am thinking the threads on the buffer tube might be smaller than the lower giving it some play to tilt.   I replaced the backing plate and castle nut but the results are the same.   Also when redoing the plate/nut I was able to twist the buffer tube about 1/4 way around and stripped some of the threads.   Guessing this is not the most robust tube for the money and should I upgrade to a BCM tube.

Has anyone else have this issue/resolve with a new (better) tube?    

Thanks in advanced.

I had one do that but it was caused by the nut threads not being straight to the flat side. When you screwed it on the tube you could hold the tube up and see the nut setting on an angle.

I have seen some receiver extensions that are mis-machined causing what you speak of.  If there is one you can remove from another rifle, or borrow from a buddy, you can verify.

That said, there are some threads here about a few Anderson lowers slipping through QC with issues.  Again, if you can use parts from a known good rifle, you can check this.

 S:  Something is definitely wrong.  The Anderson receiver may not be within milspec tolerance and your buffer tube may be of poor quality, there are plenty of those floating around.  I suggest you start by buying a new tube from a reputable maker like Vltor or BCM.  If the properly installed tube doesn't interfere with the movement of the carrier and charge handle, then call it GTG.  If you get any significant interference, then you need a new receiver.  Personally, I use only those from Aero Precision and Mega, both of which are located here in Western Washington, a gun-friendly state. - CW

Thanks guys for the response.  I will start with a new buffer tube and go from there since my threads are goofed up on this one anyways.  I have a built stag ar I can try the new buffer on if I see the same tilting.