Linked to another article BUT I present a solution in my paper Gun Shopping 2013 on building extended capacity magazines for available bolt, lever and semi-auto rifles with detaching magazines.
Another link to an article but assume they can and DO track what you read and write. The answer is to NOT use any e-mail or any computer that has EVER had your real-life identity associated or even written on in any way as the first link will be all the enemy needs. If you aren't yet doing so, get a computer w/cash, do NOT register your name on ANYTHING on it or it's programs, use wifi hotspots... if you can, use Linux or Ubuntu or some other operating system of the like.
I'd also forge alliances using 1st names only and establish a dead drop; Battlestar Galactica 3rd season the first two episodes with the Chief and the dog and its bowl show the general principle on a dead drop: have a drop, then have a "sign" that you flip when you depsoit something, and if something's deposited for you, you will know by the "sign" that there's something for you.
308 is GONE-there was the ghost of surplus past and he'd set up a shanty town and the ghost of the ar market was moving in... 223 and 7.62x39 was being cleared out.
The ONLY combat capable rifle/ammo combinations I saw there were 12 gauge shotguns and 30.06 rifles, mainly scoped bolt action rifles.
Mebbe you can get lucky on www.armslist.com but be prepared for the financial assraping.
God knows what the market's going to be in a couple months.
Happy New Year!