good idea!! i like bigbulls recomendation......to show people that though its all from a 12ga 20ga whatever you shot....that diffrent shells produce diffrent recoil......and you can explain why pretttttty easily......or to save money......do it with a couple diffrent guns instead of diffrent shells from the same gun.....like a deer rifle.....shot gun with a field load and a slug....a 22lr...a medium caliber....a BIG caliber if you can get your hands on one ect......depends on what you have to work with......depending on the foam....but hard packing foam probably wouldnt be THAT good to use....maybe some medium foam that will leave an imprint...i can see a packing foam block just shattering with a 12ga slug recoil.....or you can even forget the recoil.....and test something easy.....like muzzle velocity if you can find a conograph easily.....and i agree with bigbulls....if doing the recoil thing, id suggest something other then your shoulder.....maybe you know someone with a shooting sled type thing or something.....loooots of possibilities.......and you can explain it fairly easily...or someone here will be willing to help im sure.......if i can help explain or come up with ideas let me know......thats a GOOD project IMO...endless possibilities with a gun project.......also maybe a penetration test......man i wish i thought of this when i was in science fairs....but i was also in 5th and 6th grade i think......good luck!