The logic is that using handloads can be used against you in court.
(Factory loads not deadly enough for ya, you cold blooded killer?)
Massad Ayoob is a leading proponent of this and pounds on it all the time.
He says factory ammo can be compared forensically to determine powder burn marks, range of the shooting, etc.
Something you cannot do with reloads because there is no set standard.
My feeling is, if you are involved in a SD shooting, you darn well better be sure it was a justified shooting in the first place, and there won't be any hard questions like that.
If I blow away a BG in my house with grandpa's Model 12 and some of my trap shell reloads, I doubt there would be.
Currently, you would be hard pressed to find any factory SD loads in my house, or guns.
But thats just a personal decision I made many years ago, and may not be correct in todays kinder, gentler courts of law.
rc