In a true individual survival situation living off a pack on my back I would probably grab either my AR or my Vepr AK in 556,,,even tho I prefer 308,,,if I did not know how long it might be before I could replentish ammo I can carry a lot more rounds of 556. I would also grab a 22 long rifle pistol and a brick of ammo 500 rounds for small game hunting. In an individual survival situation with just me to supply for,, I have no problem carrying the most expensive firearms in my arsenal.
In a collective survival situation with a lot of people it becomes a whole different ballgame where a rifle that gets you by but is not the most expensive or best will probably have to do. With a defensive perimeter with a well for water or a stream or pond for water, and the ability to grow food and livestock, that is a whole different ballgame. Even though I would prefer people with different skill sets in the medical, mechanical, agricutural, and defensive skill sets, just to name a few, who have their own supplies and firearms and know how to use them and would meet at our prearranged perimeter,,,there will always be family members and friends who are not prepared for anything...For them a reliable and relatively accurate rifle will work, they dont need the best as the best for all would be cost prohibitive, but they do need a reliable and combat accurate rifle. An AR15 or AK74 would be best as there is very little recoil and they are easy to shoot easy to train a newbie on. For the more experienced a good 308 battle rifle extends the range that you can defend the perimeter out to, and for your best marksmen a couple of 338 Lapua rifles with good glass pushes the defense of your perimeter out even further for counter sniper work,, past what most guys with other calibers can shoot accurately into your perimeter. As you can see with a limited budjet you probably could not afford the best just the best quality that you could afford.
I quess I must have some Swiss in me,,,I love the idea of a National Militia with a rifle in every closet and ammo in every closet and food and water and medical supplies in every home...
At one time I was thinking of buying ten or twelve Mosin Nagants,,,they are still around $70-80 dollars on AIM SURPLUS and for $700 I could have ten rifles and the ammo is cheap...I have not done it because it is a bolt action rifle slow to fire and reload especially for the inexperienced and the recoil might be too much for the inexperienced.