Quote Originally Posted by ChrisKazoo View Post
It's this one from eBay, 50mm bore 45 mm stroke. Modified like Chris suggests by drilling port holes bigger and had to drill and tap an exhaust port at the bottom to vent it after it's fired.
http://m.ebay.co.uk/itm?itemId=190837115480
Why not use a QEV? (Quick Exhaust Valve)