Quote Originally Posted by Soonersdds
OK first off here is the setup, classic valve, HPA preset at 850 psi. I went to install the level 10 bolt on my mag and started off with the shortest spring in the kit, 1.5 carrier and 2 shims, of course lots of oil. Gun shoots consistently at 285 fps, no leaks, and bolt re-sets with no sticking. Shot a case of paint through it with no problems.

So of course I get greedy and try to use the red spring since i hear it is even softer on paint, install it with the same setup described above, gun won't shoot, turn up pressure (which uses nearly all the threading on the nut) till it does start to shoot but the gun chronos at 385 fps and is leaking out the back only. If I turn the screw down a little to stop the leak out the back the gun will not shoot.

Should I just stick with the short spring setup that worked fine, will I not be able to use the red spring, or will the new reg piston pack on the website solve this and allow me to shoot the red spring consistently at a velocity of 285-295? Thanks in advance for the help.
It sounds like the short spring is the one that works for your setup. What is the lowest velocity that the gun will shoot at while using the short spring? This will give you a good indication of how it is working. For optimum performance, the operating velocity should be set at about 20fps above the lowest value where it starts cycling.

The higher pressure that causes the velocity to be over 300 fps could be a result of the barrel that you are using. A new spring pack doesn't change the pressure that it takes to move the bolt forward, so that won't help you.