I mean, there are other factors in play. Obviously more bullets = better, if you want to always be able to shoot when it's time to shoot.
Even ignoring that, rolling more ammo dice always also increases your chance of a jam. This is as true with 6 bullets as it is with 100.
But yes, if I had players intentionally loading 6 bullets, we'd have a discussion about that. If they kept doing it, some other form of ill fate would certainly find them.