It sounds like the SU-22 isn't cycling fully. If so, the bolt is moving back far enough to eject the sent brass and strip a new round off the magazine (about 1/2 way back), but not far enough to c0ck the hammer (about 3/4 of the way back). You can confirm this by looking in the ejection port slot behind the bolt as you start to pull back on the operating handle. If you see the hammer rise up as it arcs back with the back of the bolt, the hammer is resting on the back of the bolt, and it isn't c0cked. You can eject the magazine, slowly pull the operating handle back (don't grab the unfired round and eject it) and you should be able to pull the bolt all the way back to c0ck the hammer and then ease it all the way forward again. Do this with the rifle pointed down range any time there's a live round in the chamber, just in case. If the hammer is now c0cked, it's not cycling all the way. It's probably one of the following, or a combination of more than one.
1) Low power ammo.
2) Excess friction in the operation. Is it creaky when the operating handle is cycled? Difficult to cycle? Is it clean and well lubed (outside of bolt, inside of recoil spring tube)? Any burrs on the bolt, especially the bottom, or any stray bits of flashing inside the receiver where the bolt slides? Both halves of the bolt aligned and securely tightened?
The SU-22 is accurate, so the parts are precisely fitted. With manufacturing tolerance, some will have more interference than others. Maybe your SU-22 just needs to wear in a little bit to polish the surfaces that are rubbing against each other. You might try manually cycling the action with no ammo and no magazine a few hundred times, or maybe shoot some high velocity (high power) ammo to help with the break-in process?
