I've noticed most gun manufacturers state in the owners manual that using reloads can void the warranty. My Glock owners manual certainly says that and so does my Kahr manual
So does my Springfield manual.
It is understandable since they don't want to be repairing guns damaged by your reloading mistakes.
As long as you're honest and don't try to send in for warranty repair a gun that blew up due to a reloading error what they don't know won't hurt them.
Most of my reloads are lighter than factory ammo since my goal is a power factor of 170 for IPSC competition.
A Lee 50th Aniversary kit, a set of dies, 2 reloading blocks, and a small digital scale is all it took to get me started.