Source Four Angle Sans Barrel

On several occasions, I have found it useful to hang Source Fours with no barrels in them. At a glance, this appears to produce a circle of light roughly equivalent to that of a Source Four with a 36 barrel, only without the easy ability to shutter, gel, or focus the edge. I don't know exactly, but I'd like to. Are there any specs on the beam and/or field angle of a Source Four devoid of a barrel?

Thanks anyone who knows!