The best glue gun is an automatically controlled glue gun with a sensor. Between this solution and the standard "hot melt gun from the action" are plenty of useful solutions. From the better "squeeze gun", and compressed air hand guns to fully automatic controlled glue guns.
Glue sticks and glue cartridges
11mm glue cartridges are the most common, 7mm do not actually occur industrially and professionally, sometimes there are larger extent such as 15mm, 18mm and 43mm glue cartridges. These are particularly used when refilling takes a lot of time.
In terms of ljim volume, the diameter glue stick doesn't make that much difference, in most cases it's still squeezing. More expensive hand squeeze guns can melt more glue per hour though, squeeze lighter, and pull fewer wires through a more advanced hot melt nozzle.
More advanced hand guns from Reka can be found here.
Adhesive tank systems
Adhesive tank systems can serve as the basis for an air-controlled handpistool and an automatically controlled hot melt glue gun For inline applications.