Thought on claims that DC ban had effect on ... anything.
There were a few studies that claimed to find that DC's handgun ban had some dramatic effect on homicide, suicide, jock rash, and whatnot. There have been lengthy debates over the studies' problems (like cherrypicking dates, ignoring that crime was already trending down and, in at least one case, picking the wrong effective date for the ban).
I think there is a simpler response. If this accurately reports when the chief of police said, when the handgun "ban" went into effect in 1976 there were already 41,000 registered handguns in DC.
At what rate will those deplete? A few might break and not be worth repairing, but (1) this is rare (2) I doubt the guns in DC were fired or used much and (3) since you can't register a replacement, you'd certainly repair your present one. I doubt you'd have losses of 100 a year this way. Some owners would die and be unable to transfer. Might lose 1000 a year that way. Thefts don't count, since the guns probably remain in DC. Nor do people moving away, since they're not available to commit crime, either (and not being replaced; DC at the time was rapidly losing total population).
So if we guesstimate depletion of 1,100 handguns a year after the registration stop, we'd have something like:
And the studies in question claimed substantial short term (2-4 year) declines. Even if make the gun-controller's ultimate leap of faith -- that fewer legal guns means less crime -- how could one expect to see any measurable, let alone dramatic, reduction over a period of a few years?