at the last Owensound m-14 clinic I had a problem getting a proper tight fitting gas lock, I finally torqued it down. Then I found the gas piston was very stiff and the thought of the day was its a new rifle it will shoot in. when I fired it it would only cycle properly1-2 times out of 5. So I took it apart, removed the gas lock and the gas piston slid like butter. so I figure the gas lock was too tight and causing the gas tube to deform enough to bind up the piston. removed the gas lock, fliped it over and tightened it down just to meet the gas tube, piston still moved freely, I put it all back together and it works flawlessly. 
