Bit of a sidetrack but I'm genuinely interested. In the USA could you really be sued in civil court for being involved in teaching a friend to do something that they subsequently became injured doing? If that's true how does anyone ever learn to do anything or dare pass on knowledge to someone else? Sounds surreal.
Unfortunately, you can be sued for anything and I assure you, frivolous lawsuits are filed every day.
Can you be found liable and ordered to pay money? Yes. Much depends on your level of involvement and the particular state you are in. I can not see any situation where you could be found liable for just telling someone how to do something but you never know.
Civil liability is generally based on breach of some duty, owed or assumed, and the degree to which you are at fault.
If you assume a duty to teach him to reload, and participate in the process of making defective ammo with him, and that ammo that the two of you make during the teaching process is fired and harms him and some innocent bystander, you can be held liable for the bystander, and possibly for your student.
Some states apply a comparative fault/negligence standard where a jury can apportion liability. If a jury found that you were the teacher and 90 percent responsible and your student was 10 percent responsible in causing his $500,000.00 injury, then you will be ordered to pay your student 90 percent of his total damages- $450,000.00.
Other states say that if you are in any way responsible for causing your injury, you are totally barred from recovering.
As it relates to innocent bystanders, you and your student will likely be found joint and severally liable for all injuries caused. The bystander can sue you alone and you would be required to pay all the damages. You could add your friend and claim that he is partially responsible. You both would be found responsible for 100 percent of the damages although the bystander can only recover once (100 percent).
Last, there are also some laws that make it illegal (a crime) to make ammo for others. You could be found liable civilly for violating this criminal law.
Almost a lose lose proposition teaching someone to reload.