no there's no diaphragm per se as there is in the Alpha qev. The Humphrey qev uses a piston style diaphragm that is much more rigid and reliable under high pressure

That valve has never leaked and its been in use for almost a year now. Also, the fine folks at Humphrey told me their 3/4 qev is rated like the rest on paper, but, its just for loability. The piston style qev in the valve is not like the alpha qev which uses a diaphram and is limited to what the dia...

Homemade qev air rifle build., 50 caliber bigbore.:

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The qev is 3/4 on all 3 sides for maximum flow. Qev is Humphrey and rated at 150-200 psi but easily handles 600 psi. I dont go much past that just for safety reasons not to mention it is a single shot and dumped the entire volume of air so at 600 psi it's already generating enough force to push a 30...

At 500 psi my .54 cal qev muzzleloader launches a 300 grain patched slug at about 1000 fps. Barrel is rifled from a knight black powder rifle. 3/4 inch qev is piloted by a 1/4 inch ball valve. Gun is very accurate. This is my first post, any feed back is welcome.