Not all bullets are created equal. I have a load developed for their 124 gr JHP that runs great in my race gun and is very accurate. Each manufacturer's bullet of the "same" weight and profile will vary somewhat and will often have different bearing surfaces, which affacts friction (and therefore velocity). Even if I went to someone elses 124 gr JHP, I would still need to do some chrono time to make sure I was making major, and I don't have the time to do that. Not to mention having to re-zero because it would be likely that a different bullet would have a different point of impact.