evidence: Gun control advocates say mandating a window of even a couple of days between the purchase of a gun and taking possession can give more time for background checks and create a "cooling off" period for people considering harming themselves or someone else. Studies suggest that waiting periods may help bring down firearm suicide rates by up to 11% and gun homicides by about 17%, according to the Giffords Center. [...] California has one of the country’s longest waiting periods — 10 days. That did not stop more than 1.1 million people from buying guns last year, which was just shy of the record number sold in 2016. Gun sales nationwide, meanwhile, surged to record levels last year amid pandemic-related uncertainty. [...] Gun rights groups, including the National Rifle Assn., oppose waiting periods. The group points to 2018 federal firearm-tracing data that shows the average time between first retail sale of a gun and involvement in a crime was nearly nine years. They also argue that waiting periods create a delay for people buying legally, while leaving illegal weapons transfers unaffected.