There are many opinions on what the best BO/survival firearm would be . Some would say a 22 , or a shotgun . Others might suggest some sort of military type rifle - AK, AR , SKS etc. My personal choices are a 38/357 revolver and a 38/357 Marlin lever rifle . I also have a 12GA. shotgun but I might leave it behind because the ammo weighs too much . The revolver would be the first thing I grab because I feel it is important that you have something that is concealable. I think the 38/357 is a good all around caliber and fairly common . I also feel that having a common ammo for rifle/carbine and handgun is a good idea .