[BillCA]

I think the OP was asking what the results of a gun ban would be and perhaps how enforcement would be carried out.

Let's take it from the top. Congress passes a law outlawing individual citizens from possessing firearms. Additional laws burden any firearm seller with huge amounts of paperwork and approvals before transferring a gun to, say an armored car company.

• Companies like S&W, Ruger, Glock (Georgia), et al, lay off anywhere from 70% to 95% of their employees.
• About 96% of the small & medium businesses such as distributors and dealers close.
• Ancillary companies like Burris, Leopold, HKS, Bianchi, Safariland and others shutter their doors and lay off workers.
• Ammunition companies lay off 90% of their workforce as demand for ammunition drops dramatically.
• After a brief spike in sales during legislative debates, Alliant, Hodgon, Winchester powder plants are shuttered or reduced to a small operation. RCBS, Lee, Dillon, et al close.
• Contract prices for US Military small arms and ammuntion increase approximately 350%.

Secondary effects:

• Loss of revenue to insurance companies who charge high premiums for gun-related business liability insurance. Other business insurance rates increase to offset the loss.
• Some layoffs at packaging & printing shops since thousands of product boxes are not being produced.
• Unknown economic losses as workers cash in stocks to survive and shareholders of now worthless Ruger, S&W (etc) stocks push court actions.
• Decline in machine tool orders for steel working machines and tools.

Enforcement effects:
I doubt the gov't would implement a large-scale plan to confiscate firearms from the general public. Instead, this is what I think they'd most likely do...

• Use BATF registrations of Class III firearms to notify owners of a "turn in date". Those who don't, get a visit from the BATF SWAT team and are used as "object lessons" to all other gun owners.
• Use state and federal registration records to identify people who own "large collections" of firearms -- i.e. more than 100 guns. Notices are sent to them demanding they arrange a "collection date" with the local authorities. Those who refuse are arrested by the local SWAT teams and prosecuted.
• Agency videos of these busts are given extensive air play on media outlets to show that police are enforcing the new gun laws and charging people with felonies with huge prison terms.
• Known belligerent owners who are likely to engage in a firefight may be given that chance just so BATF can show justification for using light armored vehicles and destructive tactics "as a lesson" to others.
• As the number of "large" collections diminish, they refocus on "sizeable" collections -- anyone with 25 or more guns. Lather, rinse, repeat.
• US and local district attorneys provide high profile press conferences when "illegal gun traffickers" are finally sentenced.
• If you use a firearm in otherwise legitimate self-defense, initially the tactic will be to fine the defending victim between $5k to $10k for possessing the gun and that's it. After 2-3 years however, the fine remains plus 5-15 years in prison.
• When owners of less than 25 guns are to be taken down, instead of direct assaults, owners will be asked to appear before an IRS tax audit (with their spouse) or some similar arrangement (Jury duty, building permit review, etc.). While there, SWAT teams serve a search warrant (if such is still required) on an empty house or one containing only other family members. The main belligerents are out of the way while their property is seized and they are arrested away from home.
• Joe Sixpack with his nightstand .38 is left alone. If he ever uses his gun, he goes to jail. On top of that, like the U.K., the thug who forced him to use his gun (or the thug's family) can sue the crap out of Joe Sixpack and win.

Crime Rises
As criminals see the citizenry become defenseless they will change their tactics.

• Muggings on the street will become more common.
• Carjacking to obtain desireable autos increases.
• Home-invasion style robberies take a huge jump since citizens are less likely to have a gun. The thugs will have their guns with them, of course.
• Rape increases, especially kidnap-rape crimes.
• Gang activity increases and spreads to formerly "nice" neighborhoods. Gang members intimidate anyone they please and are still armed with guns.
• New guns are produced in a clandestine "cottage industry".
• Sales of "protection dogs" increases.
• Sales of alarm systems skyrockets.
• More affluent communities become "gated communities" in an effort to reduce crime.
• The "Kitty Genovese Syndrome" is repeated hundreds of times as citizens hearing cries for help don't even call 911 for fear of "getting involved" and worries over retribution.
• State and local governments pass more laws aimed at reducing crime. Prohibitions against carrying a knife with a blade longer than 2", prohibitions against OC spray, stun guns, Tasers, etc. leaving even more citizens defenseless.
• The wealthy retreat to gated communities with gated properties guarded by high-tech and armed guards, possibly with K9 units.
• Numerous wealthy persons obtain one or more good quality "black market guns" early on, one that isn't traceable to them. After an incident, they'll turn it over to police and say they got it from the thug (in a struggle or by striking it out of their hand). The thug won't be able to deny it either.
• Crime sprials out of control in many areas of major cities. Thugs become bold enough to assault and rob patrons on mass transit without fear of interference or apprehension. Parking garages with any form of security charge astronomical rates.
• Employee costs skyrocket in some cities due to the level of crime and employees not wanting to live nearby.
• Health care costs jump (even more) as companies pay for crime victim injuries, sometimes into the six figure range.
• The government increases taxes to cover rising costs of crime and increased payouts for law enforcement fatalities (due to gun battles with gangs).
• The Police Chiefs petition congress to make new laws to make it "easier" for them to arrest and prosecute thugs. Congress kills entirely the "fruit of the poisonous tree" doctrine, the Miranda warning and lowers the bar for extended police searches.
• U.S. Police state begins emerging in full.

There... did I miss anything?