Depending on your method of travel you might be able to carry more than I gun with you.
Tis why I picked a .357 Carbine as my bug out gun. Takes the same ammo as my handgun. With .38 special loads in it good for small game , with full .357 magnum loads it will drop deer, bears (If I do my job)or 2 legged varmints if needed. Ammo is reasonable in weight. At one time .39/.357 ammo was very common, prob #2 behind the ole .22 Long rifle.
The 1 Gun for everything problem.