Those rifle owners, who thought that the rifle would be the target of the ire of Politicos, decided they might like to learn how to use these new-fangled doo-dads... so they bought ammunition for them.
They bought more ammo. Then still more.
The surplus .223, 7.62NATO and x39/x54 dried up in a hurry. Add in a war, and prices for new ammunition almost tripled in the last 10 years.
Gun grabbers realize there is a new glut of EBR's out there, with bullets for them. Their goal now is to regulate/ban/tax/hinder the ammo out of existence, helped by your desire to train and familiarize yourself with your rifle.
Don't help them.
The best political statement you can make right now regarding firearms (aside from membership in AT LEAST 2 prominent organizations of your pick) is to shoot a LOT. A lot of .22.
Trick out a .22 to handle like your EBR. It may be a 10/22 rigged like an M14/M1, or it may be a Ceiner conversion for your AR. Learn mag changes, learn to shoot from something other than the bench, and learn to make HITS rather than just to shoot for the thrill of shooting.
Take a rifle class. Appleseed, NRA High Power, Gunsite, Frontsight, anything... as long as you:
1. Build your skills.
2. Network with other shooters and likeminded folks.
3. Become involved in local politics as a result. ALL POLITICS IS LOCAL. Lexington and Concord were local.
Keep familiarity with your EBR, but keep your ammunition reserves at a secure level. Shoot just enough that you can afford to replace.
Then go shoot that .22 some more.