Suspect your spring is too long. Easily checked. Get the piston without spring and lock it into trigger to mimic a cocked rifle. Use a vernier to measure distance from inside face of piston where top hat sits to face of trigger housing where rear guide locates. Then measure diameter of spring coils and times this by number of coils. Add on thickness of top hat and rear guide flanges and answer will be clear. V-Mach springs are thicker than original so will take up more space when fully compressed! Also note that you need a couple of extra mils free space to allow cocking as when rod engages trigger sear it needs to go past it's resting or cocked and locked position.
A brace of TX200's
Ex PCP *****!