I saw mention of that on an NRA email link. Main point I noted was this only taxes the people that are least likely use guns for violence, law abiding gun owners. I doesn't tax illegal guns at all.
Why is it that liberal's gun control initiatives nearly always target law abiding gun owners rather than illegal guns? I guess there is always the bent thinking that if 1000 firearms sales are stopped and only 1 of those was to a crook, then it was a good law.