Gun Safety: Not Sorry Act of 2021 This bill modifies firearms-related background check requirements for transfers involving a semiautomatic firearm, silencer, armor-piercing ammunition, or large capacity ammunition magazine. For transfers by a federally licensed dealer, manufacturer, or importer to a private party, the bill lengthens the number of business days—from three to seven—that the federal licensee must wait for the background check results prior to completing the transfer. For transfers between private parties, the bill establishes a minimum seven-day waiting period.