Amount you can carry
Fighting between the big-round and small-round groups reached a peak in the early 1960s, when test after test showed the .223 Remington (M193 5.56×45mm) cartridge fired from the AR-15 allowed an eight-soldier unit to outgun an 11-soldier unit armed with M14s at ranges closer than 300 meters. U.S. troops were able to carry more than twice as much 5.56×45mm ammunition as 7.62×51mm NATO for the same weight, which allowed them an advantage against a typical NVA unit armed with Type 56-1s.
https://en.wikipedia.org/wiki/7.62%C3%9751mm_NATO#Adoption_in_battle_rifles
Interesting chart there too about how much ammo you can carry in a 10kg load of magazines.
260 rounds of 762 NATO
620 rounds of 556
360 rounds of 762 Soviet.
Long Range Effective Accuracy
On the other hand, once you get out to like 300 yards/meters, lighter rounds will get tossed around by the wind, but personally I was having success with very heavy 85gr Open-Tip Match 5.56. But that's premium stuff, and standard 55gr and 62gr projectiles were very hit or miss shooting prone at a 8-inch target.
Recoil and Quickness of Follow-up Shots
.308 out of an AR-10 feels like twice the recoil of 5.56 out of an AR-15. It's not fun. The gun weight too feels like twice as much. If I'm lugging something around I know which I'd prefer.
What are your thoughts? Also, is the new larger US military rifle/caliber contract won by SIG Sauer dead in the water? I think it is, except maybe for specialized roles like DMRs.
The first gun you get should be a basic AR-15 with a reliable red dot
Then you get a hand gun, and the best one-size-fits-all handgun is a glock-17. Good ergo, good quality, wide parts availability, wide magazine availability.
Then you can get whatever else you think is cool, or just buy ammo.
Make sure you've got the important stuff, though - A good quality sling for the AR, a bunch of good quality magazines that you've tested to make sure they feed reliably, secure storage for your guns, a good holster and a shooting belt for your sidearm, at minimum a chest rig for magazines for your rifle, a real big-kids first aid kit with hemostatic dressings and a tourniquet, some way to carry at least 3l of water around with you, good close toed boots or hiking shoes. Just having a rifle isn't going to do you any good if you don't have good shoes. The accessories are important, too, and the cost adds up even if you're sourcing surplus or used gear.
Pretty good advice. I basically did that but got the G19 instead of 17. I think a defensive long gun needs a light as well.
This kind of advice seems to focus on SHTF open carry, but, honestly, I think comfortable everyday conceal carry gear is more important, even in a SHTF scenario it would be wise not to draw attention by open-carrying. I think most threats we face now and in the near future are best addressed by conceal carry. Pepper spray is the first and foremost thing, more important than a gun, more useful, more versatile for threatening situations that are not apparently deadly force, more accessible, less liability. Pocket flashlight with a momentary switch are very handy and very important for identifying what is and isn't a threat. If one does decide to carry a gun, get a size and holster setup that one would be comfortable carrying every day, because it's not providing anything by being left at home because it's too inconvenient to wear.
Strong agree on pepper-spray. it's so much better than a gun in most situations. Also strong agree on having a good weapon light for your rifle and a good flashlight for day to day stuff.