Reading through some of the more recent posts on stars reminded me that a star gun is essential for evaluating compositions and I need to put one on my shopping list.
From what I've seen online, there seems to be three distinct types out there and offered by reputable suppliers of pyro materials.
The first consists of a number of different diameter tubes welded on end to a plate and states that the length of the tube is 9 times the diameter so, for a 3/4 inch star, that would be a 71/4" long tube. This seems excessive to me just to fire one star.
The second is of the same general type but the tubes are all the same length regardless of diameter. Looking at other items in the photograph, I'd estimate that the tubes are something like 4 - 5 inches in length.
The third type uses round aluminium bar with holes drilled down the length of the bar. No dimensions are given but looking at where the fuse holes are, it looks as if the holes get shallower as the diameter decreases. This would be in keeping with the sizes of drill bits which also get shorter as they get thinner.
As I do have some limited metal working facilities and skills, I feel confident that I could make one of the later type so t is of particular interest.
I would be interested in other peoples views of the above and, in particular any thoughts on the safety and effectiveness of the three types. Perhaps those of you who already have a gun would be kind enough to let me know what length the tubes are for 3/8", 1/2" and 3/4" diameter tubes on your device as these are the only sizes that I'm interested in at the moment.