It used to be a Federal Law that if the NICS did not respond in three days you were good to go. DE changed it to 25 days. So if the FFL doesn't get a proceed they have to hold the firearm until they hear or 25 days passed.
I think this is the relevant info.
http://www.delcode.delaware.gov/title11 ... ndex.shtml
Code: Select allTITLE 11 Crimes and Criminal Procedure Delaware Criminal Code
CHAPTER 5. SPECIFIC OFFENSES
Subchapter VII. Offenses Against Public Health, Order and Decency
§ 1448A Criminal history record checks for sales of firearms [Effective until Oct. 30, 2018]
(b) No licensed importer, licensed manufacturer or licensed dealer shall sell, transfer or deliver from inventory any firearm, as defined in § 222 of this title, to any other person, other than a licensed importer, licensed manufacturer, licensed dealer, or licensed collector, unless and until being informed that it may "proceed" with the sale, transfer or delivery from inventory of a firearm by the Federal Bureau of Investigation (FBI), NICS Section pursuant to the request for a criminal history record check required by subsection (a) of this section or 25 days have elapsed from the date of the request for a background check and a denial has not occurred.
EDIT: I see what they did there is another section after the above for 10/30/2018 onward.
Code: Select all§ 1448A Criminal history record checks for sales of firearms [Effective Oct. 30, 2018]
(b) No licensed importer, licensed manufacturer or licensed dealer shall sell, transfer or deliver from inventory any firearm, as defined in § 222 of this title, to any other person, other than a licensed importer, licensed manufacturer, licensed dealer, or licensed collector, unless and until being informed that it may "proceed" with the sale, transfer or delivery from inventory of a firearm by the Federal Bureau of Investigation (FBI), NICS Section pursuant to the request for a criminal history record check required by subsection (a) of this section or 25 days have elapsed from the date of the request for a background check and a denial has not occurred.
“I prefer peace. But if trouble must come, let it come in my time, so that my children can live in peace.” -Thomas Paine