As a side note... Dummy rounds are used to test correct feeding and not necessarily ejection. This is because dummy rounds resemble a loaded round and not a fired round which is what is normally ejected.
In another words the dummy round might feed okay but not eject properly. On the other hand it might eject corerectly also but isn't guaranteed. I have a AK-74 that feeds dummy rounds without any problems but sometimes hangs up during the ejection process. In live firing there are no problems what-so-ever.
When making dummy rounds make sure to drill about 4 holes in the case so they can be seen from any side. Polish any burrs off with emery cloth. This provides a visual indicator that helps prevent accidently grabbing a live round that may be lying around(could be a live round with a light primer strike). A small piece of wooden dowel is also put inside to replace the weight of the powder charge and to add another sound indicator. (the weight inside is important because some guns will jam because without it the round is end heavy and doesn't eject true) The dummy should weigh and balance the same as a live round to test gun funtionality.
I left out a few things yesterday... I made dummy rounds for all the guns I worked on in gunsmithing school. So I could use them as snap caps I took 1/4 nylon rod and turned it down to primer size and glue it in the primer socket (electric drill lathe). Them I sanded it down flush with the cartridge base. A primer will dent to the maximum after a couple snaps and put undue strain on the bolt assembly. I also used brass black to change the color of the brass (pre-steel case days). I also only used new cartridges, no fired ones.
Thanks so much for the information guys! I'm going to do a little more research on making my own dummys. Like color, shape, weight and etc. If it's something that is of very little cost to me I'll send you all one. No charge!
As a quick note, dummy rounds should be used for form and fit only. Snap Caps have a spring in the primer pocket to ABSORB the firing pin impact. A dented primer will not absord the impact, and it will allow the firing pin to move forward completely, as in dry firing. This is not a bad thing on most of todays modern firearms, and most others. However there are some firearms out there that have older more brittle firing pins that may be damaged by dry firing. Also if the firing pins may already have damage, dry firing my make it worse. Snaps caps are cheap compared to repair costs. Not everybody can do their own smithing.