To be a true scientist you need a question (how many jackets does it take to stop a bullet?), predictions (at least four jackets), a hypothesis (this will totally work), experimentation (shooting your friend while wearing multiple jackets), data analysis (bro, did it go through?) and finally a conclusion (yeah you've been shot). 

So technically, even though they are idiots, these guys are scientists and the kind we think governments should be giving more funding. 

Though they started off with a simple premise, their execution is a bit lacking (in jackets) as the bullet test clearly shows their friend taking a round to the back, though it does look like the jackets helped dampen the impact, this guy still needs to see a doctor. 

So in conclusion, is it possible to stop a bullet with a bunch of jackets? In theory, yes, but I wouldn't try to test this one yourself.