inonickname wrote:Wrong, if you have enough of an acceleration force, and the balloon is a loose enough fit it will become deformed and possibly pop. It's like getting a water balloon, and squeezing it in your hands. It pops, doesn't it?
Therefore it would be good to make the balloon a good enough fit in the sabot so it can't expand further than the rubber can manage, but can still discard the sabot. There's where your challenge is.
Doesn't matter what the acceleration is, if the balloon doesn't touch the barrel, and if the sabot doesn't have any sharp edges, the balloon won't brake. You can accelerate a water balloon at any number of G's and it won't pop the balloon.
Making the sabot the same size as the ballon is trivial, just use a plastic cup.
The only time you have problem with G forces poping a water balloon is when the resting diameter of the ballon is a tiny fraction of the barrel diameter. If you put a 1.5"D ballon in a 2" barrel there is no way it'll pop in the barrel if properly saboted. There is virtually zero force on the ballon rubber regardless of the acceleration as long as you are not talking about something like 1"D ballon in a 12"D barrel.