This past summer my bro-in-law purchased an norinco sks from another member here on the forum. When he took it to the range it would only fire one shot and he would have to work the slide manually. He brought it to me, I had to remove the pins to remove the gas tube assembly( it was completly seized ) I got it clean and operational but it is missing the secondary piston that goes to the receiver. I've found the piston at several places but have not been able to locate the spring for it. Does anyone know of a good source for these?