Model 98 trouble

I searched but couldnt find a solution to my problem..... Im pretty new to paintball so bare with me if I dont explain well enough!

I have a Model 98 and when I shoot it will spit out about 2 balls about 10 feet then the hammer will go back to the uncocked position. Sometimes just one ball

It does it on all of my c02 tanks. And the o-rings are fin on them. Sometimes it will shoot fine then all of a sudden it will start shooting bad. I took it apart 3 times de- & resembling everything but nothing so far. ALL my screws are stripped now cause my dumbass self over tightened them... I didnt hear no air-leakage anywhere. I tried messing with the velocity screw but nothing yet. The little yellow thing that holds the ball in place seems to be fine too... At the most it will fire up to around 10 times then the hammer will go back down to the uncocked position as I sayed earlier. Even when its shooting my balls wont go anywhere, sometimes they fall right out of the end of the barrel when i pull the trigger. And like i sayed my velocity is turned up.

Thanks for all the help guys.

If you have striped the screws that hold the Power valve in place, that is likely the cause of your inconsistency. If the screws holding the power valve in place are still tight then look at replacing the Power spring (rides the rod behind the hammer).

I believe when you say the marker "spits out" two balls then goes to the Un-cocked position, you do mean that you get two short range shots in a row and after the second shot the hammer is un-cocked.

This indicates that not enough pressure is coming out of the power valve. If you have a full tank, there are virtually only TWO things that cause such performance. As I said above, loose or missing  power valve bolts which allows the power valve to move away from the hammer thus reducing strength of the impact on the pin valve and reducing gas output.

If the power spring is old or you have installed a stock that slightly changes the way the power spring is compressed you will get the same low power/ failure to cycle performance. When there is a low power hammer blow to the valve there is insufficient gas to both propel the ball and to push the hammer back far enough to engage the sear and stay cocked.

I looked. Its not backwards.