Bill, As you know it is a gas piston. I can't give you the pressure number, unlike a spring it is a constant pressure but smooth until cock. Not as bad as a Diana 350, I have one of those. That 20 in the name stands for foot pounds of pressure !!
Hey Mike, The Kittery Trading Post in Kittery ME is showing the ASP 20 synthetic in stock for $349.99. (free shipping) they are probably 15 min from the SIG factory (I'm about 30 min). kitterytradingpost.com or cal them at 888-587-6246.Bill.