Everyone is a law abiding gun owner until the moment they aren't...and that's not an acceptable standard.
Although most crime is not committed with guns, most gun crime is committed with handguns. pages 1 & 2
By definition, stolen guns are available to criminals. The FBI's National Crime Information Center (NCIC) stolen gun file contains over 2 million reports; 60% are reports of stolen
handguns. page 3
Stolen guns are a source of weapons for criminals
All stolen guns are available to criminals by definition. Recent studies of adult and juvenile offenders show that many have either stolen a firearm or kept, sold, or traded a stolen firearm:
According to the 1991 Survey of State Prison Inmates, among those inmates who possessed a handgun, 9% had acquired it through theft, and 28% had acquired it through an illegal market such as a drug dealer or fence.
Of all inmates, 10% had stolen at least one gun, and 11% had sold or traded stolen guns.
https://www.bjs.gov/content/pub/pdf/GUIC.PDF
A 2019 survey conducted by the Department of Justice (DOJ) found that some 43 percent of criminals had bought their firearms on the black market, 6 percent acquired them via theft- and 10 percent made a retail purchase – 0.8 percent purchased a weapon from a gun show.
https://www.foxnews.com/us/where-do-criminals-get-guns