From what I have read on all the prepping sites. 1,000 loaded rounds per rifle and pistol and 10,000 22LR for each 22 for a SHTF minimum. 22LR might be used far more for food gathering than the others. However, semiautos might require far more rounds than say a bolt gun. With each new brass case, one should be able to reload 10 times. Thus 10 times as many primers, powder for the required and bullets.
I know someone who has like 100 357 loaded rounds in a 50 cal ammo can. Also inside is 1,000 primers, 1,000 bullets, and 1# of powder. Also, a Lee hand loader for the 357. This is his grab and go SHTF can. He has a 357 rifle and pistol. He said, in a SHTF situation, he would reload immediately after shooting once he had time, keeping his 100 always loaded. This is bare minimum thinking, but not a bad idea. He liked the idea of both handgun and rifle using the same cartridge. This could also work for 44 mag, 9mm, or 45acp, if you had one of the Marlin camp carbines or other rifle to go with it.