But everyone knows you can't claim self defense if you use reloads.

But out of respect to the OP, I will give a serious, but short, response to the question.

Who says it's not a good idea? And what are their qualifications to say it?

Many people say it will cause malicious prosecution. Where is the proof they are basing that on? If prosecutors could use that argument and make it work, there'd be tons of evidence to back it up.

In Mas Ayoobs case of New Jersey vs. Daniel Bias, Mas' testiomony wasn't permitted to be heard in the court. From the little bit of information that is available online it appears to be because it had nothing to do with the case. The defendant went to jail for murder but it had nothing to do with the fact that he was using handloads or even if he in fact was using handloads. It didn't matter. The testimony wouldn't have contradicted any evidence that was pertinent to the case and appears to have been an attempt to create doubt in the minds of the jury.

But, there is/are place(s) that do forbid the use of handloads for CCW permit holders. It is written into their laws and everyone needs to know for sure what their local laws are. But even then, if you do shoot someone with ammo that is not "legal" that will not change the question of "were you justified in taking a life?", it'll just add a seperate charge on your docket.