In a nutshell: don't work on an graded project with a 3L. In my 2nd year, I had an assignment where our grade was given to the group as a whole that we worked in. We worked in groups of 2. Our professor paired me with a 3L. I ended up having to do all the heavy-lifting. The guy was slack as shit.
I don't know if his effort was because he was a 3L but I suspect it was. He once commented that it took him over 4 days to respond to an email because he was "busy." (I'm just a 2L myself. Like I'm sitting around yanking it)
I hope he was an outlier. I'm no gunner but if your performance affects another's grade, decency and common courtesy should compel one to put in at least a half-assed effort.