[ChuckHam]

For true SHTF situation when you want things to go bang every time and have the least possibility to jam I would recommend:

30/30 Lever action
12 gauge pump
.357 Magnum revolver

[T.B. Yoits]

For true SHTF situation when you want...

30/30 Lever action
12 gauge pump
.357 Magnum revolver

For SHTF, the 30/30 and .357 limit your options of using your allies' or your enemies' ammunition.

For SHTF, you might want 9mm, 5.56, 7.62 x 39, or 7.62 x 51 instead of .357/.38 and 30/30.