Quote Originally Posted by Solvo View Post
Why would the vent be in a part of the cylinder that the seals pass over?
The output vent to the storage is most likely in the end, I dare say the intake is likely piped to that same end, or possibly even just a valve in the piston itself. It doesn't have to be in the sidewall of the cylinder, there are other options!
This. While not familiar with multipump guns, I know that with multipump lots of other stuff there is often a simple valve in the piston itself.