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How to make a balanced spool valve? For a PVC airgun, need quick release valves.

I'm trying to make a 50 caliber airgun, but this time with a better valve. My previous one had a ball valve, and it's sticky, hard to aim, and just troublesome. I did a bit of research on airgun valves, and it seems as though the balanced spool valve is a good one to try. However, all the searches seem to be focused on the discussion, not the making of the valve. I'm going to be using PVC, hopefully 3/4"+ for the air chamber. Anyone know how, or know a better valve? Thanks! 

use a LITTLE BIT of wd-40 and twist it in