First, let's get the messy facts out of the way.

Federal Courts aren't going to sit on their hands while this happens.  
Second, the Republicans won't sit on their hands either, so a deal must be struck.
Third, the Courts, require the DOJ in the form of the US Marshals, the FBI, (and now the whole umbrella of DHS) to enforce Federal Court Injunctions.

 

Act I Step 1:
The POTUS issues a EO, commanding the BATFE to "audit dealer records" - ie, look for "strawman sales" by reviewing each of the dealers Form 4473 records.  This is actually easier if the dealer has adopted the eForm 4473

For handwritten forms, an OCR scanner would be carried, the form scanned, and information corrected on a laptop prior to the next scan.

What can't be done? Is hold a news conference.  It can't be done by BATFE Agents alone, as this demands too many bodies in too many locations, at the very same time.  

We as a nation, will have to let a few things slide, while various agencies supply personnel to work with BATFE Agents.
Yes, a same day, nationwide "I'm here to review your records".  Close every single gun seller that day, days, or week(s) until the audit is complete.  Sold a hundred guns in your entire existence? We'll be gone by 4pm today.  Sell a hundred per day?  You can re-open after the end of the year.
It'll put you out of business?  Impact hunting season and holiday sales? (Which next to DiFi's failed AWB II is the most money you make in a year?)  That's sad.  CLOSED... can read GONE OUT OF BUSINESS.  We score that as a win... you and your fellow death merchants can retrain as Baristas.

So, now we have ALL the records scanned... and a comprehensive list of who purchased what gun where.  Those are sorted for make and model.

Shotguns.
Semi-auto shotguns.

Rifles.
Semi-auto rifles.

Rimfire rifles.
Semi-auto rimfire rifles.

Handguns.
Semi-auto handguns.

(save ALL of this data for later)

Step 2: permit the dealers to reopen - however, now the eForm 4473 is 100% required,
and in a slight tweak, batch processing is done once a week, where the forms are uploaded "to the cloud".
(as-if 'the cloud' isn't on those servers already)

Step 3: Prioritize you list.

 

Act II Step 1:

Strike a deal with the Republicans.  For public consumption, word it as ambiguously as possible... as was the ACA (just pass it and we'll find out what's in it) and stuff it into the next Continuing Resolution.

On this 11th day of December, 2015 this 114th Congress does hereby resolve to instruct the Department of Justice to audit all Federally Licensed Firearm retailers for compliance with 18 USC as condition of their license, and direct all necessary resources to do same.  The Director of the BATFE, the Attorney General of the United States, and the Director of Homeland Security may adopt policies and procedures necessary to effect this Congressional mandate.

About those Republicans:
First, they're really not that happy with massive civilian gun ownership, they just like the cash from the pro-gun crowd.  
BREAKING NEWS!!
They like the cash from Wall Street, and Corporate America better.

Give Congress the choice between:
a) massive controls on financial transactions, killing their benefactor's proven-risk derivative market
- or -
b) massive (armed) civil unrest when we pull a Greece and shove a total economic collapse onto the American taxpayer?
Rationed water, electric, heat, food and fuel and a 65% tax on your income.

Everyone other than a Tea Party Republican will choose to eliminate the risk of option b.
The motion will pass.

There's going to be a political quid pro quo. I'd hang my hat on "illegal immigrants" taking it in the neck. How and why, is below.

 

Step 2:
Federalize ("second") the National Guard of the respective states.  Just as we could send them to war in Iraq, we can deploy them as deputized federal agents. One BATFE agent to 3 or 4 guardsmen.

 

Step 3:
Go door-to-door with your list of gun purchasers, and get access to the guns.  A massive VIPR-like sweep.
No gun? Where is it?
Who has it? Where's the paperwork?  No gun, no paperwork?  
You're coming with us... the weather in Cuba is fine.
Sadly, it appears the nationwide cell phone network is down, unless you're using a government contract cell phone.
Yes, surprise is key.
Oh, by the way... you have ID don't you?  Born here?  Let's run that ID.
So... you're here on a visa, that expired in 2003.  
You're coming with us, the weather in Minot, North Dakota is fine.  
There's your required quid pro quo to the Republicans.

 

Step 4:
Anticipate the Federal Court Injunctions.
Injunctions which are enforced by... the DOJ and US Marshals.
Who are preoccupied in carrying out the mandate of Congress.  
You've reached the DOJ, leave a message at the beep.

 

Step 5:
Mistakes happen.
Somewhere in the process, an "honest mistake" happened.

Knock, view, verify and record the presence of the named firearm in the possession of the named owner - or find out who has that firearm - was misinterpreted.

Knock, bash-in the door, verify the presence of, and confiscate the named firearm - became the process.

Rules of Engagement were defined as: "take no incoming fire - lethal means authorized".
A few "rogue operators" decided that if it looked sketchy, breach the door after the flash-bang grenades, and engage anyone seen with a firearm in proximity using lethal force.

 

Step 6:
The number of confiscated firearms becomes a problem.  National Guard units are directed to turn the contraband over to Active Duty Military Police.  Certain weapons may be re-purposed by the government, exported to allies, used by agencies, or stripped for parts.

Light alloys are put into a grinder, steel and stainless steel are cut with a plasma torch to render  non-salvageable (prevents theft in transit), then taken to a smelter to be melted down.

 

Step 7:
The higher Federal Courts, and perhaps the SCOTUS weigh in.

Answer A: "It's gotten out of hand, and we can't reach all of the field units... your order to cease is understood and complied with at the Executive Level.  The logistical issues however, preclude prompt compliance in the field. The majority of units are out of contact, operating independently beyond range of communications."

Answer B:
Arrest those Judges.  What part of Congressional Mandate didn't you understand?

There's going to be some issue, with a few mouthy Governors complaining about "...patent misuse of the Guard, violation of the Constit..." Yep.
We're sorry, the Governor's new conference has encountered technical difficulties.  
To Jamie, and Sports!

It's amazing what a FBI Agent can do for video production: "Cut the feed, NOW. Otherwise? You're coming with me, the weather in Cuba is fine."

The prevention of an armed civil insurrection requires a total lockdown on the ability to communicate.  The NSA knows this. Anyone studying the Arab Spring knows this.

The email servers of the various pro-gun groups "appear to have sustained a prolonged DoS attack by some overseas entity in Asia".

Facebook decided that a new version of their photo and written content filter was worth Beta testing, and all gun-related images and commentary ceased to be shown.
Yes, the "nipple filter" took down the gun fetishists.

 

Act III. The SHTF.

Step 1:  Eventually, it all comes to a halt.
The Nation awakes to a new reality. Your armed-to-the-teeth white male neighbor, is now gumming on a lone Winchester .30-30.  
The massive number of Guardsmen and Federal Agents go home, taking all the ammunition with them.  "By mistake."  
"30 Cal M1 or .30-30 Winchester, how the hell should I know?  I've only shot a M-16 in Basic. Sarge said 'get the ammo too, all of it' and I did."

No self-loading handguns, shotguns, or rifles exist in lawful civilian hands.
In certain areas, the gunfire continues, as does the presence of Guardsmen, Agents and Police.  
The ROE remains: Take no incoming fire.

A well publicized CRIMINAL AMNESTY program is offered.  Turn in your semi-auto, no questions asked regarding who it might have killed, or how you derive your income.  
As certain acts (suicide in particular) continue, the decision is made to remove all handguns from civilian possession.  
A 1 year Amnesty is offered.  If we have to come for it?
It will be with lethal force.  Suicide-by-Cop.  
It's a price, it's paid once.  
"Handgun suicides were virtually eliminated in a three year effort."
The suicide rate remained unabated, and went up in the next economic collapse.
"What can you do?  We tried. At least the guns are gone."

Gun makers are given a chance to merge, develop next-generation firearms for the military, or go out of business.  
The few remaining gun shops offer your choice of single barrel, double barrel, or 2 round capacity pump-action shotguns.  
Single shot, bolt-action, double-barrel, lever or pump-action high power rifles, with 4 or less round capacity.  
Wow... how Steampunk!
This is what my great-grandfather must have seen back in the early 1900s!

Legacy shotguns and rifles with greater magazine capacity can be altered "plugged" to meet the new limit.  The plug must be welded, machine-pressed, or epoxy fastened to prevent removal.

 

Step 2: A black market of gun imports is created. Mexico is now a donor-state.
That's managed by combining BATFE and DEA with exponential success.
You can still get a 9 millimeter handgun with 15 round magazines, it just costs $6,000 for the gun, and another $10 per round for the ammo.  The price of Cocaine and Heroin go up as well.
Guns come from Brazil, and arrive on the same truck, boat, or airplane as the drugs.
Logistics baby, logistics.

 

Step 3: The SCOTUS get's it's day.
The POTUS retires by then, lauded "for his courage, however misguided".  
Congress is rebuked.
Contrite, it offers to "work towards a solution".
Nothing much happens, as there's no means of recompense.  
Return your gun to you?
Ah... here's a baggy of shredded metal.  My dbad.

Eventually in the year 2061, when many of the affected citizens are dead, Congress passes a Resolution offering "an official apology for the so-called unconstitutional gun confiscation, coincidental loss and damages".
No funds are appropriated.
Japanese-Americans, knowing of their history under the Roosevelt Administration, merely nod with a wry smile.

 

Act IV: Disarm the local cops.  Either return them to revolvers and possibly shotguns, or transition to disarmed local policing.  That precludes raiding the police station for weapons.
Serious incident? The State Police can render tactical aid if needed.
State police can be armed with appropriate levels of modern weaponry to end any threat to law and order.  That's how it's done in Europe, a closely supervised select few have serious weaponry at-hand.

THAT is how you get it done.  ALL of it done.

 

Act V, an Afterword:
The danger? Is in the American people finally understanding they live in, and pay to support, an Oligarchy of the Corporate Interests, by The People, for the Corporate Interests.  Pigs to slaughter, cows to be milked.
Use whatever metaphor you choose.

The danger of knowing that the distinction of Democrat or Republican has little meaning.
Neither respect the limits of the Constitution, and pass laws exempting the government from adhering to the Constitution.  (do you see the irony in the DOJ website banner)

It's your choice of white or wheat, comprising the same, shit sandwich.

No matter, the means of revolution has been disposed-of.
Welcome to the new American Century, one where your vote doesn't count, you'll shut-up and do as you're told.

The massive coordinated workers strike? Never happened. Filtered from existence.
The spontaneous occupation of the streets and squares?  Went great for a while, then it went predictably when the Oligarchy tired of non-compliance.

Tue Oct 06, 2015 at 6:00 AM PT: Tuesday @ 0800 observations:
using this diary's poll data, with a standard math principle rounding of numbers,
~10% of replies are for some form of drastic action, just not whole hog.
~10% are for "get 'er done" and go for ALL of the semi-automatics, and maybe more.
A further ~10% is for a total gun confiscation.  Every. Single. One.
That's 29% in true numbers.  
1-in-5 respondents are willing to kick doors in, and get it done today.

This past August, HuffPo claimed 67% of HuffPo readers seek some vague form of greater gun control
http://www.huffingtonpost.com/...

71% is for politics-as-usual, working within current restraints/constraints.
Fight the NRA. Contribute to Democrats. Volunteer. Pack the SCOTUS, and change the meaning of the Second Amendment back to the way it was.
ie:  The various guises of Government, have the right to a citizen militia, and to the guns required to equip said militia in time of conflict.