You mean a gate valve? (Planar motion)
@ Simon - my answer is "yes." Plot the valve rate (% flow and distance) and look at look at the really low-lift attributes. They're different and the compromise is distance to max flow. I have a hard time believing that you can change the seal geometry of any poppet gun design and not affect the perfomance without adjusting throw to accomodate the additional cross-sectional distance you have to overcome with a radial seal. Almost the entire firing characteristic of the gun boils down to how this single valve performs. All supporting sub-systems converge here as well.