My SHTF ammo supplies, in rough order of escalation:
1) 30-round mag of Hornady 75g TAP, always stays in the rifle (bolt closed, no round in chamber). 1 loaded mag in my pistol and 1 backup mag always nearby, but the pistol stays chambered (and holstered).
2) 4x 30-round mags TAP + 2 loaded pistol mags, in an ammo pouch thingy, stays with my shooting gear, always close at hand either at home or in the car (moves around a bit)
3) 4x 30-rnd of TAP + 1x 20-rnd of plain green tracers + 2 more loaded pistol mags, stays in my Light BOB backpack, which is always in my car (which is always wherever I am). The Light BOB comes in from the car sometimes, but I never leave it home when I'm away, unless flying commercially.
4) 240 rounds IMI M855 on strippers in bandoleers + 100 rounds pistol ammo in boxes, in my Heavy BOB (which can only be transported realistically by vehicle, but has much more serious supplies - box of MRE, decent stove+fuel, gallons of clean water, water filtration system, large tent, axe, large blankets, fishing/hunting gear, heavy rope, survival medical supplies, several good survival books so I don't have to remember everything myself, etc, etc). Stays at home unless it looks like I'm gonna need it.
5) 1k XM193, 1k Q3131A, 1k IMI M855, 500 pistol ammo, + however much TAP and target/range ammo I have leftover at any given moment (probably totalling roughly another 1k), in cans at home. If bugging out by vehicle these would probably go with me anytime the Heavy BOB gear would, but it all depends on the situation. Some situations might be known to be temporary, in which case maybe I don't need to lug all that ammo around.
After re-reading what I just wrote, I think I might be overdoing it a bit. But then again, by arfcom standards, I'm sure I'm quite underprepared