Actually that'd be ~22.1 seconds of fire, at my computers repeat rate holding down r got me to a count of 864 in ~29 seconds, round it up to 30 for the B and t. 

Therefore typing only takes ~136% of the time to type characters than it takes a GAU-8 to fire that many rounds. 

The 1% figure would require a typing duration of &gt;36 minutes to be accurate.