Everyone should write a letter to ATF and/or Congress. Here's mine.

"Dear Sir or Madam,

I am writing to express my opposition to the banning / reclassification of .223/5.56mm ammunition. This is common rifle ammunition, not something associated with crime. Changing the law based on political whims makes it difficult for the gun industry as well as law-abiding gun users.

I urge you not to let this common ammunition to be banned.

Sincerely,

[My name]
[My home address]"

Obviously don't use my exact or the language from the article. I hope they get countless messages from individual e-mail accounts, not organizations, saying in our own words we don't want the ban.

A more direct route for sending your feelings (tho same wording as in OPs link) to the ATF is http://savem855.com/

Yes, a bit humorous to claim that it's a cop killer bullet or that AR pistols (An AR with a short barrel and ugly rear end) poses such a hazard since most have been around for some 20 years or more without a huge spate of cop killings.

I am personalizing the language so it doesn't sound like a duplicate and sending it. Everyone should take a minute to write a polite paragraph about why the proposed ban is wrong and send it to the address in the article.