I have a Chinese SKS that I received from my nephew months ago in the form of a barreled action only. I put a colapsable fibreglass stock on it and all went smoothly up to that point. Took it to the range and it would fire only one shot at a time but not semi auto. I am new to SKS's and someone mentioned a gas tube ? Perhaps it would help to get one of those cheap owners manuals for $4.00 with an exploded view. Thanks for any suggestions you may make. It is clean but perhaps the gas tube is clogged ? Would that effect the semi auto cycling ?