I have a general practice of purchasing and installing the buttstock as an assembly, with the tube, buffer, spring, spanner nut, etc. Less likely to have issues such as this. I know at this point it's like hindsight being 20/20, but it comes from lessons learned. I had an issue a while back where I got the stock (Magpul CTR) from one source, and the rest from someone else. The fit was so tight I ended up taking a wire wheel on my drill press to the stock for a few seconds, then greasing the stock up to get the stock to slide back and forth smoothly. I told the supplier,and they no longer buy from that vendor. I decided at that point it wasn't worth the money I saved to buy the stock separate from the rest of the assembly.