Some states have one-day waiting periods, others have three-day waiting periods, while in others, owners have to wait ten days until they can go home with their firearm.
Given that many gun-related homicides, mass shootings, and suicides are committed in moments of extreme rage or depression, making someone wait a pre-determined amount of time between expressing interest in owning a firearm and receiving their weapon could offer a cooling-off period in which the assailant changes their mind.  It would also drastically reduce suicide deaths. Most suicides have been contemplated for less than 24 hours and are a compulsive decision. Being able to immediately purchase a firearm provides suicidal citizens with an accessible means to commit suicide, which is fatal in 90% of cases (jumping is only fatal in 34% of cases and drug overdoses are only fatal in 2% of cases). States with waiting periods have 51% fewer firearm suicides and a suicide rate 27% lower than states with immediate purchase laws. Waiting periods also reduce gun homicides by 17%.  A waiting period also provides a wider window for the authorities to actually carry out a thorough background check. It also doesn’t go against the constitutional right to bear arms. It is a form of gun control without restriction. Citizens are still freely available to buy weapons.
Waiting periods put citizens at risk. Consider a situation where a citizen felt threatened and believed that their husband was mentally unstable and plotting to kill her. She cannot go to the police on a hunch without evidence. But she is vulnerable and knows she needs to protect herself. She drives to her nearest gun shop, only to find that she must wait three days before she can bring her handgun home. That night, her husband kills her. This argument was what prompted lawmakers in Wisconsin to consider revoking the mandatory 48-hour waiting period on gun sales in the state. Instant background checks now make waiting periods redundant. There are also already mechanisms in place to prevent someone buying a gun and committing a crime of passion. Most gun sales cannot be completed in under an hour. This is plenty of time to cool off. If a person still commits murder after an hour of cooling off, the crime was premeditated and not a crime of passion.
[P1] Waiting periods allow more time to carry out background checks [P2] They also allow people to cool off, leading to fewer crimes of passion and impulse involving guns. [P3] Therefore, there should be mandatory waiting periods.
[Rejecting P1] Background checks can now be done instantly. [Rejecting P2] Making people wait puts vulnerable people in need of protection at risk.