A couple of thoughts; when I taught self defense with a handgun the last time I actually got statistics to cover the cost, the average "good shoot" of an attacker was going to cost the individual defending themselves $12,000 in legal expenses - that was in 1992! The exception was a few states in the south and the west that held self defense in the respect it deserved. But that's only the police and prosecutor's part of the action. As has been rightfully mentioned, anyone can sue the person defending themselves in civil court, and that's a huge can of worms and $$$.
To those who have been advised by local law enforcement in classes or as a result of direct questions and been advised that it doesn't matter if you use handloads for self defense, be thankful that you live in an enlightened jurisdiction. The problem generally isn't law enforcement, it's the next step, the District Attorney's office and it's prosecutors - in many places in the northeast and in states like Maryland, Illinoise, New York and California, there are individual prosecutors who will go to any length to discredit and then charge an individual involved in a legitimate self defense shooting, including playing the handload card. Fortunately, good defense attorneys have learned how to deal with that version of attack on their clients and it doesn't usually make it into court, even when the prosecutor does get the case into court (remember that $12,000 in 1992? That's where it goes). And the latest approach of such unscrupulous, gun owner hating DAs? Carrying a reload for your carry gun! First they'll try to paint you as Rambo for carrying, say, a high cap semi auto with a double stack magazine, then they try to reinforce the Rambo image by nailing you for carrying a loaded spare magazine. Good defense attorneys know how to counter this, too (start by asking a testifying office what the capacity of his duty sidearm is and how many reloads he carries), but the point is, the damage may already be done where the jury is concerned, and their opinion is what matters, whether based on common sense or not. Think being painted as Rambo for carrying a reload for your carry gun is a myth? Judges have been known to NOT allow expert testimony on this subject, so you better know what the local police carry, and that certain firearms malfunctions can only be handled by a reload. An example of both painting a legitimate shooter as Rambo for carrying an extra magazine and not allowing expert testimony at trial is "Commonwealth v Pepicelli. In short, arguing about whether handloads are permissible in self defense is hit or miss, depending on where you are likely to get hauled into court in the aftermath of a legitimate self defense shooting, but it is one more tool that could be used by an unscrupulous prosecutor that is easily avoided, and avoiding it in a criminal case will help make the ambulance chaser's work in a civil suit more difficult.
Be careful out there and watch your flanks.
Mike