Black Friday is typically the biggest day of the year for gun purchases and therefore background checks, fueled by holiday shopping and the fall hunting season.
Every time someone tries to buy a gun from a federally licensed dealer, a background check is processed.
An interested buyer needs to give their ID to the seller, fill out ATF Form 4473 with personal information such as age, address, race, and criminal history, if any.
Then the seller submits the information to the FBI via a toll-free phone line or over the internet, and the agency checks the applicant's info against databases. The process can take as little as a few minutes.
It's unclear just how many firearms were actually purchased on Black Friday because initiating a background check doesn't guarantee a sale.
This year, March had the highest number of firearm background checks collectively, surpassing every other month at 2,644,851.
The FBI's National Instant Criminal Background Check System, known as NICS, records the number of background checks. Since the system was started 21 years ago, the FBI has conducted 330,067,172 background checks.
CNN's Aaron Smith and Jose Pagliery contributed to this report.