Motherjones also fails to recognize that MANY states already have mandatory "cooling off periods" where if you buy a gun on say Monday you can't pick it up until later in the week.
"As with many states, Illinois has a mandatory 72-hour wait period between the time a person purchases a handgun and the time he can take the gun home from a licensed dealer."
In most cases, these waiting periods are for handguns and not rifles or shotguns. The law is not to prevent suicides but to prevent 'crimes of passion'. There would be very little difficulty in someone killing themselves with a rifle or shotgun, although it isn't as easy as putting a handgun to one's temple.
Introduce background checks and you will reduce the number of suicides, more likely than not.