Actually the .22LR cartridge is stuffed to the bullet with gunpowder. you simply cant put more in there. Its just a tiny case that doesnt hold much is all.. If you want more power in a rimfire, get a .22 mag or a .17HMR, or better yet the ol 5mm rimfire mag, more powerful than both the .22 mag and the .17HMR, but ammo is 'spensive and hard to find, and still you have to own 4 separate firearms to use all 4.
Most of us would agree that the last part is mostly a good thing..