Stargrave crew have various costs, Recruits and Runners are free, so with only a limited amount of credits to spend, most starting crews will contain a number of each.
Runners are unarmoured, which means they are not weighed down so can move faster than Recruits.
To give a consistent look, the first three are armed using the revolver arm from the Crew sprue (so from three sprues).
This Runner was made using a body from the second Crew sprue.
And a group shot.