I've spent probably about 45 minutes farming printers for blueprints, but I have still yet to get one, if you could like increase the chances for blueprints, that'd be great, because literally nobody has blueprints anymore
I'm not sure if Premium printers have a higher chance than regular ones to drop BPs, but last time I spoke with drew I think the chances were all the same.
As for the exact value it was either 1% drop rate or 5%. (I might be wrong)
I mean i farm printers quite rarely but when i do all nighters i seem to get about 30ish bps but most nubs will sell them cheap and i know some people farm printers but rarely make guns so have a large pile up i would say ask around and you could buy a lot.
You have a 2.5% chance of getting a blueprint everytime you withdraw cash from your printer. That means if you just let them fill up and collect now and then you won't get blueprints that fast, but if you constantly collect from them once they have money its better chance of getting blueprints.