Note you will need to make the flash hole larger, or the primers will stick out enough to bind things up.
For balloon popping loads my brother loads a primer with a few grains of Triple 7 FFFg topped off with grits (Cream of Wheat) Sealed with a bit of soft bee's wax. They will pop balloons out to about 10 feet or so. (Lead Free primers are what I would suggest if used inside to avoid breathing lead particles.
No matter how many times you do it and nothing happens it only takes something going wrong one time to kill you.