I thought it was that, but that should only happen with a sticky firing pin, shouldn't it? Mine appears to be moving freely. I did end up taking my type 97 into the gunsmith and they couldn't narrow anything down, said they never got it to slamfire using the ammo I was using and other brands. It happens fairly frequently too. Tried to sell it but nobody wants it. I don't really want a slamfiring gun so I dunno what to do with it.
To make the rifle Canada-compliant, Norinco had to remove a number of components designed for the Automatic version. One of these components was the device that kept the hammer from falling until the bolt has returned to battery. Because of the strange recoil impulse caused by the rocking recoil buffer in the stock, not only is it an easy gun to accidentally bumpfire, it is also possible to pull the rigger and release the hammer before the bolt has completed it's forward cycle. This will
not cause an out of battery detonation, but it can cause a slamfire.
The main issue is the bolt's long, slow travel time. There's a few things you can do:
1. Grease the receiver rails. This has the double effect of speeding up the bolt and decreasing the "lock time" - the sometimes noticeable pause between trigger pull and the bang
-1b. If you're willing , I also took 1000 grit sandpaper to the rails and contact surfaces of the BCG and hammer. (Just a little, not even enough to affect the finish on the metal) Mine slides like glass.
2. Replace the recoil spring. The factory spring on the Gen 1 is pretty weak. Get a standard weight AK recoil spring and snip off a few coils (I cut off 6). Speeds up the bolt and reduces felt recoil.
3. Practice better trigger control. Keep the trigger firmly held down after each shot. If you hold the trigger too loosely, the odd recoil impulse can cause you to inadvertently pull it again.
Hope this helps.