The answer especially for pistol bullets, is it is not abnormal, you will find premium bullets will be closer in weight, premium rifle bullets are usually very close, both to the weight advertised and from bullet to bullet, Sierra, Nosler, Barnes, Berger etc... They are close enough to use as a rough check of your powder scale, set it to 168 grns and drop a 168 Matchking into the pan, and it will show if your powder scale is having any trouble.