Basically yes, I usually lop off about 4 inches, but instead of riveting, use self tappers instead, that way its easier to open up and replace the wadding if and when you need to.
what these boys said^ lol i found that when cutting it leave it all together dont take it apart before u cut its much easyer that way coz the inner pipe is held nice n tight and almost a perfect length (bit of tweaking will be needed) its a nightmare to cut that inner pipe by hand out of the box if ur using axesaw
