Am I Breaking Any Us Laws Shooting My Rc Tank's Air Powered Potato Gun With Rounds That Explode On Impact?

Location: Missouri, USA

I built a 300lb rc scale tank that's about 3.5 feet long and gave it a compressed air main cannon (pretty much a potatogun but breech loaded). Its just a thick steel pipe that I load variuos scale tank rounds into to do scale penitration tests in wood and aluminum plates. So far I have just been using mini 3d printed or solid brass rounds.

I checked my state and federal laws and it seems perfectly legal to build, own and operate an air powered projectile launcher.

The part im hoping to get advice from you kind folks is, I was hoping to test some small scale tank rounds that were filled with black powder and maybe small metal fakes to give a firework like pop when the round impacts the test armor. It that illegal? The rounds that do the firework like explosion will be made out of clear plastic and are just for educational purposes. The black powder charge will be less than 0.5 grams of reloading black powder. I am hoping to make educational videos on historic evolution tank ammunition and armor.

Im only seeing state and federal laws saying "exploding ammunition" for "firearms" are illegal but also only is some states (but I couldn't find if they were illegal in Missouri). But they specifically state "firearms" and Title 18 United States Code (U.S.C.), Chapter 44, S 921(a)(3) or 26 U.S.C., Chapter 53, S 5845 seem to say this is a legal "spud gun".

And yes all testing is done with the highest levels of saftey in mind (no living creatures within a 40 acre lot next to another empty 40 acre lot and an 1nch of polycarbonate blast shield between me and the steel test chamber, along with me being hundreds of feet away during the testing). I was a nuclear saftey engeer so I know a good amount about saftey engineering systems.