I just got a stag lower with a mil spec buffer tube. I wanted to put on an ACE ARFX stock I had laying around to see how it would look. It went on fine. However, when I went to remove, it wouldn't budge. It feels like the stock is lodged in my upper somehow. I tried pouring CLP on the buffer tube, still no dice. What are my options with regards to removing the stock withouth destroying the buffer tube?

Thanks!