I think it would even be impossible in the physical sense. What would be the plan - to go door to door in 100 million homes?
It's a multi-year process.
Years 1 and 2 setup legal gun registration, background checks, additional training courses, databases and start the gun buyback programs.
Buy back programs continue in years 3 and 4 along with distribution of information regarding the new legal requirements and limitations and registration and permit processes and waived costs of said registration.
Year 5 confiscation and fines when caught with.
Year 6 jail time when caught with.
Would cost billions of dollars. But at the same time it would be economic stimulus in a way. It would also save money in the long run. It's not impossible, but more costly to do it in the United States due to the immense number of guns. Would be even more feasible if police resources moved from clamping down on lesser drugs to gun control.
For reference, here are the terms of owning a Gun is Australia
How easy is it to get a firearm in Australia?
A spokeswoman for the Australian Institute of Criminology told SBS a person looking to own a firearm in this country needs both a licence and a permit.
To obtain a licence, they must be:
18 years or over
Judged as a fit and proper person
Have undergone a firearms safety training course and;
Have provided documentation about the storage arrangements in which they will secure the firearm.
Licences will not be granted to people:
Under the age of 18
Who have been convicted in the previous 10 years in the current or another state/territory of an offence prescribed by the regulations
Is subject to an apprehended violence order or at any time in the previous 10 years has been subject to an order (unless the order was revoked), or;
Is subject to a Good Behaviour Bond to an offence prescribed by the regulations
"In NSW and South Australia, persons under firearm prohibition orders are also ineligible for obtaining a new or renewing a firearms licence," the spokeswoman said.
"Suspensions and revocations of licences occur when subject to an AVO or other prescribed reason."
http://www.sbs.com.au/news/article/2014/12/18/how-easy-it-get-gun-australia