If I were building an AR-15 today, I’d do it in 6×45. That’s a wildcat caliber based on the 5.56 mm. It’s necked up to 6mm. Other than the neck size, it’s the same. You can use the AR platform and regular magazines. No need to modify the bolt or other critical parts. Just a different barrel.
The 6×45 throws a heavier and bigger bullet giving it better stopping power than the 5.56 mm. But it has much less recoil than a 7.62 NATO. You need to reload.
From Death Wish III:
“You load the shells yourself?
“Paul Kersey: Nothing’s too good for our friends”
I’ll respond to the objection I anticipate: It’s not a standard caliber. Preppers should only use standard calibers!
My take on this: Scavenging for ammo is overrated. When you run out of your stock, you’ll be out. Load up 400 rounds and you’re good to go. Bigger danger: mixing up 5.56 and 6×45. That would be bad.
If money is super tight. Get a Ruger 10-22 for $200. Yes. A 22LR. In a riot, you won’t be fighting attackers in body armor. A 22 LR coming from a carbine length barrel is nothing to be sneezed at.