first things first.......
you ever hump with that much ammo? what other gear will you need to take? how fast will you need to move? in the absolute worst case scenario how long could it take to reach the BOL? do you plan to drink or eat along the way? how bad can the weather get in your AO? would you survive the worst that the season had to offer?
don't want to sound harsh but these are some serious things to consider.
ammo is heavy and taking along *extra* weapons just adds unnecessary weight. now considering that in a SHTF/zombie bug out you may need to deal with some of societies lowest element and the walking dead i would not consider the .22 an option. sure it's fine for brain eaters but crack heads that have managed to dodge the brain eaters is another story.
if a scoped bolt gun is needed to engage the threat you can just as easily avoid said threat.
a 12ga is big, slow and heavy. what it produces in damage isn't enough to make up for the drawbacks.
from your house to the BOL, how far is it? what is the terrain like? are you walking 2 days in nothing but forest or will you need to E&E in the burbs? if it's the latter of the two and it takes two days in perfect conditions i would add 1 or 2 more days to your travel time to be safe. my BOL is 15 miles from my house, once upon a time i could run that far. no water, no weapon, no gear but i could get there in a hurry. i now plan on a 3 day hump if i had to go on foot. i would rather not be seen or heard along the way.
don't need much food for 3 days but water would be nice. the down side is that it's heavy. taking a filter? is there a place to get water along the way? what if it's compromised? a group of guys hanging out there or a dead body in the water source? i trust my filter but not that damn much.
did i mention that ammo is heavy? you'll want the most bang for your buck (or pound in this case). a weapon in 5.56, 5.45, 5.7 would be ideal in a BO situation. it gives you lots of firepower in a small, light platform that can reach out 200+ yards. if all else fails then 7.62x39 would be a close runner up. the mags are too heavy but if it's all you have then i say use it.
the .50 isn't going to be of much use if you need to BO but it could be handy to have at the BOL.
one rifle (SBR preferred) and one side arm is all you should even consider taking. stash more mags and ammo at BOL along with other weapons and gear.
YMMV
AR in 5.56 and G17 FTW