I recently received Mark's Carbon Arms one piece tube and went to install it on my 26" VM field gun. While cranking down on the tube to meet up with my receiver I noticed it would never meet up. So I grabbed a Craftsman strap wrench and cranked down, still no go. Took the tube back off and scraped on the receivers threads for a couple of hours to clean them up and still no go. So my gunsmith and I drilled a hole in the top of the tube to insert a long screwdriver for leaverage and still no go. At this point I was getting very frustrated and didnt know what to do next since my stock tube could be inserted and be flush while cranking down with one hand. So I had one more idea up my sleeve, I took it home and put the one piece tube in the freezer and left it in there over night. The next morning I gave it one more shot before I had to call Mark again, and by god it actually worked. I managed to get this tube flush inside my receiver and I was so proud of myselft. So if anyone has any trouble I would suggest trying this tip first before you make a mess of things like I did.