I just finished modding an old longshot CS-6. I removed the air restrictor, trigger lock, bolt lock, and clip lock, plugged the leak hole in the breach, and replaced the spring. For the new spring I used an 11" cut-to-length [k25] spring from McMaster (part #9637K25), since this is what I saw many people recommend on this forum and other places and videos online.
However, after I reassembled the blaster and tried to fire it I immediately noticed that pulling the bolt back is extremely difficult. I basically have to pull with both hands and support the gun against my chest in order to get the bolt all the way back.
But the bigger problem is that the plunger doesn't lock back. I pull the bolt back as far as I can (which is within a couple millimeters of as far back as the handle can go) and the plunger just doesn't lock in place as it is supposed to (I hear and feel no click and can feel that the bolt is still under pressure). I don't for sure know exactly what is happening since I can't see inside the gun, but I am assuming that the spring is so strong that even though the bolt handle is all the way back the plastic inside is bending in such a way that the rear tip doesn't reach the trigger plate.
Both the above problems seem to indicate that my spring is way too powerful. But I am confused since this exact spring was recommended by almost every post or video I looked at about longshot modding. For example, in this video coop uses this spring and doesn't seem to be having the same trouble I am in priming it. I did try removing the new spring and putting the old one back in to make sure I didn't mess something up, but it works just fine with the old spring.
What am I doing wrong? Am I using the wrong spring? Did I miss anything?