Shtf????? Way to broad. There are so many scenarios for this.
One thing you need to ask yourself is "What are your personal capabilities to keep the firearm fed and for how long this needs to be done." IMHO the SKS is fine as long as ammo is available. Then there is the issue that the rifle is a semi auto and cases will be lost pretty regularly. You won't be shooting it on a range or from the bench. How mobile are you intending to be??
The SKS is a fine design but it certainly isn't noted for being accurate. Same goes for rifles such as the Mini 14/30. Some of the AR offerings and other such higher end rifles can be seriously accurate both with and without optical sights, buttttt they are HEAVY and weight can be a serious obstacle when it comes to what a few pounds of saved weight can be replaced with.
This is just IMHO, but you must get your head around the fact there won't be any chances for resupply of ammo/parts etc. Take a long hard look at that situation and ask yourself what situation you're going to prep for. Short term such as getting stuck in the bush for a few days, mid term such as flooding/snowed in with help on the horizon or long term which includes a complete collapse of government and worse.
IMHO a bolt action with plenty of loaded ammo, which can be 223 rem or 7.62x39 mainly because they're readily available in bulk at present time. There is one other very viable option and that is a 22 rimfire, either in a magnum or standard long rifle format. Shotguns are OK but ammo is heavy and expensive.
It all boils down to this. When the SHTF and there is no viable option for resupply, you have what you have and only luck and by golly along with some other unpleasant options will be your only hope. The cartridges that are the most popular will disappear first. That includes, 22 rim fires, 223rem, 7.62x39, 308Win, 270Win, 30-06 Springfield. The other less popular cartridges may be around slightly longer but the supply will be extremely limited. If you will be mobile, things such as fuel for vehicles will dry up the first day, so you will be limited to what you can carry without hurting yourself. Your load will consist of light shelter, food, heavy coat which will double as a sleeping bag, couple of liters of water, ammunition/firearm. One alternative which is very good is a rifle matched to a pistol with the same cartridge.
If you're going to be static in a hidden or defend-able position then you can stock it with several years of supplies or just about whatever you wish including reloading supplies. The biggest issue with such a location is that survivors will be looking for such places and as such they are extremely susceptible to attack. Don't kid yourself for an instant that such situations will bring out the stellar qualities we have been socially programmed to believe. One good example was the last huge US and Offshore Tsunami incidents. Many of the local police/soldiers bugged out to be with or look for their families instead of doing their duty. NOOOO, I don't blame them one bit. The survival of their families may have been absolutely dependent on them being there and getting them to safety. Horrible position to be in.
OP, you really need to do a lot of indepth due diligence before setting up such a kit. You also need to find out if you have friends you can TRUST in such a situation or the likelihood of a knife between your ribs in the middle of the night or somewhere along the trail is almost a sure thing. DON't tell ANYONE where your bugout route ends. If other survivors, usually starving, know the location???????????????????
This sounds paranoid but if you've ever experienced a complete societal break down it quickly becomes obvious what needs to be done and what changes need to be made to your personal attitude. I can just about guarantee that after a month every stranger and even friends you may run across will chew off the hand that feeds them.
