A link to SAAMI...
http://www.saami.org/specifications_...tion/index.cfm
SAAMI is a voluntary industry organization that ammo manufacturers belong to and voluntarily abide by SAAMI standards.
Some manufacturers do not belong to SAAMI or abide by their standards. It is usually these that show +P or +P+ loads for calibers that don't officially have +P designations recognized by SAAMI.
tipoc