#4 very dangerous because the pump can easaly exceed
your guns max air psi in a very few strokes compared to a compressor which is way slower on compressing air into a gun compared to using a booster 3 0r 4 flicks of your finger on my boosters 2800 psi to 4000 psi depending on youy guns air chamber .Not trying to say you are rong but the info is not the some for all boosters especially mine which is very good at boosting and scavaging its drive air source.