|Since there will be ammo shortage and new gun control laws in the US, it would be wise to invent replacement for unreloadable .22LR.
Concept #1: steel case and annular primer
This concept is consisted of two pieces of steel parts that can be screwed together, while an annular-shaped primer made of copper can be replaced. The cartridge can be reloaded after the primer is replaced.
Concept #2: center-fired .22 cartridge
.22LR is too small to receive center-fired primers in the market, and it requires newly-designed, re-designed firearms or conversion kit in order to use it. A new standard of small-diameter primer must be introduced in order to advance this idea. Most current .22LR guns can be converted to center-fire without too much trouble.
Concept #3: electro-ignition system
This could be the most craziest idea, but it has been done by Remington and can certainly be implemented. By eliminating primer all together, and using high-voltage ignition, it makes reload almost too easy. Heck, if done right, it can even fire black powder loads. Unfortunately, it requires drastic change of firing mechanism, which means new firearms in most cases.