I was trying to do some target practice this morning and my rifle had a malfunction for the first time in 15,000 rounds through it. I fired 6 shots that I had left over in my hunting ammo magazine, reloaded with the old standard target reload of M-118 bullets and LC brass. It fired one then on the second one it didn't cycle. I ejected the empty manualy and tried again and it kept doing that for 6 more rounds. I took the rifle out of the stock and looked it over then took out the piston and wiped it off with a rag and put it back in. after that it worked flawlessly for 50 more rounds. I just did a good cleaning 2 weeks ago including the piston. it only had 40 rounds through it before this happened. I cleaned the bore last night with sweets 7.62. as always I closed off the gas valve first then when I was done I opened it back up and with the op rod back ran a pipe cleaner up through the hole to make sure there was no solvent in there. This rifle has never failed to work perfectly before and I am realy curious to know what happened. I am a gunsmith and have been shooting 14's for 20 years or so. This one for about 10 years. anyone have any Ideas? My rifle is a norinco receiver with a douglass heavy weight match barrel and GI everything in perfect condition. It was below 30 degrees this morning when this happened but I have shot it in 30 below weather without problems before. The wind was also howling about 40-50 MPH and actualy whistling through the flash hider. My son got a kick out of that.