I've read here and there that the Tapco gas tube and piston are both sized slightly larger in diameter then their stock counterparts. I'm looking to confirm if this is so, because I have an SKS that seems to have a gas tube that is slightly too large for it's piston. This apparent mismatch in size seems to be causing a failure to fully cycle.
I tried the test where you hold your thumb over the end of the gas tube with the piston inside it, and then turn it vertical to see if the blocked air pressure causes the piston to slowly glide down (which indicates a good fit), or drop quickly with the normal speed of gravity because the air has room to quickly get past the piston head (which is bad - too much room), and it is the latter situation (too much room) that holds true for this gun.
All of which makes me think that this mismatch of gas tube to piston size might possibly be because the tube is one of the slightly larger Tapco replacement tubes, while the piston is still the slightly smaller stock one.
So my question I guess is this, are the Tapco gas tubes and pistons indeed slightly larger in diameter, and if so then by how much? Are there specs out there somewhere on the Tapco parts vs the stock ones with respect to gas tube inner diameters and piston head diameters that I can reference to check and see what I've currently got?
If it is a larger Tapco gas tube mismatched with a smaller stock piston that is causing my failure to cycle, then it's possible that all I will need to do is put a matching Tapco piston in to get the gun cycling properly once again, but I'd like to be able to check the sizing before I start spending good folding money for a part I may not need.