May I ask what's the intended purpose? There are a few ways to make cat's sneeze loads but what you want to do with them makes all the difference in the world.
If what you want is a large bore rifle that you can shoot in your basement, maybe try the plastic projectiles that you shoot with a primer only in the case (Speer made them I think). You can use hot glue sticks instead. Cut little pieces as close to the same length as possable, they are ususally perfect in 44 cal, Or use a bullet mould andfill it from the hot glue gun. With just a primer they will shoot fairly well across a room with enough power to punch a hole in paper or knock down a soda can. Glue fowling isn't as problematic as you may think. If it builds up at all, you can take it out with regular hardware store denatured alcohol solvent. It doesn't disolve the glue into a mess, it just breaks it's bond so it pushes out with a patch. The plastic bullets are reusable and not too much money, the hot glue is dirt cheap but not reusable unless you are moulding them.
If you're looking for a load with a little more punch and still want to keep it indoor quiet, try light loads with a ball. A ball is lighter than a bullet in the same diameter and has less surface in contact with the bore, so less resistance.
I did some work a couple years ago with boring out cases to accept a 203 primer and soldering a piece of brass tube into the case to keep the ball from rolling back. I was using bottle necked rifle cases, so the tube was a needed piece. I made a few in 7.62x54r that worked pretty well. I don't remember the exact size balls, but I do remember that it was a bit tricky finding lead balls that wouldn't roll right through the bore or get jammed in. I do know I found some that worked. You may be able to do something with a .410 shell, a primer and some light projectile through a 45-70.
Big thing is to always check between each shot when you are playing with cat's sneeze loads. If you're using a single shot like a Handi or a rolling block it's easy to peek down the pipe, a trapdoor is a little harder but you'll think of something. When I was playing with a mosin nagant the temptatuion to not look was tough. I made a point of shooting light metal targets so they made a "gong" sound so I knew the ball had cleared the bore. You can also use a light. You don't have to look through to see if light shined in one end shines out the other. Be safe, have fun.
All that said, a 22 with cb's or a pellet gun may be the thing. It all gets back to what you want to do with it......
