I've got some really good pix showing several angles - enough to get very close measurements. I also printed pix of the gun to actual size - based on pix I have of her holding the gun perpendicular to her gauntlets. I know some for-sure sizes (i.e. Leeanna is 5'6", her gauntlets are approx. 5" long and I know the size of the black hose connectors and hose itself ) and based my measurements on that. From this - i determined that the gun barrel is about 10.5" long.
How are you going to do the front of the barrel? I could never get a really clear picture of what was going on at the business end.