A friend of mine is working on a bunch of short films and I found that a lot of the special effects involving guns and gunshots tend to use either explosive squibs or air-powered squibs.
The problem is, compressed air squibs can be really unreliable or produce a shitty effect, along with needing a lot of tubing and whatnot fed under the actor's clothing. Don't get me wrong, the Sanjuro blood fountain was great, but I'm not trying to go full /a/ memeshit with gunshot wounds.
Explosive squibs apparently cost a lot and there isn't much information available towards making your own that are people-safe.
What I was thinking was to take 12/20/.410 ga shotshells and cut them down to various lengths along with removing most of the powder, leaving just the primer and maybe a small amount of propellant. The modified shell would have a plastic sac filled with fake blood might just use the real deal, it's free after all that would be ruptured by the plastic hull and hopefully spray everywhere.
This would be actually set off either by a fuse wire fed into the back where the primer would be, thus necessitating more powder, or by a spring-loaded shortened firing pin. The shotshell would be put in either a short metal pipe (probably with half the shell exposed to prevent too much presssure buildup) or a PVC pipe.
I've got a mechanism conceptualized for the firing pin setup but can't be fucked to draw it right now.
All this crap would likely be threaded in to a smaller metal plate or held in place by duct tape/thermoplastic on top of one of my 6x6 armored plates. I think the body armor behind it should be sufficient to prevent any potential damage to the actor wearing the squib, but it might be worth investing in an extra set of level III soft armor just in case.
Do any of you have experience with special effects? Is this a horrible shooting accident just waiting to happen?