It is my understanding that a Nics check cannot be delayed " Indefinitely". This provision was put in to prevent the NICS System from being used as a restraint to lawful purchases. ATF Form 4473 ( rev AUG 2008) seems to confirm this.
vis Q 21c offers 4 options from NICS to the initial INquiry
Proceed - Denied-Cancelled or Delayed.
Q21d reads If Nics or state response was delayed the following response was received from NICS/State
Proceed-denied-cancelled or No resolution was provided within 3 business days.
Q21e ( Complete if applicable) After the firearm was transferred, the following response was received from Nics/State on: date Proceed - denied- Cancelled
In other words if NICS cant respond in 3 business days you are free to pick the gun up( if 3 days is permitted in the state where you live) and you are not otherwise legally disqualified
