I propose the following.

1. Upon reaching the age of 18, every able-bodied male receives military equipment. They also get a range pass, where they can go to any gun range and redeem their coupons for ammo and time at the range to practice with their arms. In fact, NOT going to a range and shooting X amount of rounds in a period of time could be considered a crime, punished with PT and more range time.
2. Every adult male is also required to attend mandatory training, perhaps every 6 months at first, then every year once they reach 26 or something. There, they are trained in the proper usage and maintenance of their military arms. They are also trained in how to keep in physical condition.
3. It will be a crime to not have your military arms and armor in good working condition, as well as proper physical condition, with a stockpile of plenty of ammo which the government will provide. We can test them at regular intervals to ensure they are keeping fit and keeping armed.
4. If someone is to become disabled, then they can return their military arms and armor and be relieved of duty. Similarly, once they reach a certain age they can opt-out and return their equipment and be relieved of requirements.