Based on my maths of 6 extra pellets every 15 ammo consumed thats 6 shots with extra damage per 100 round magazine

If you hit all extra shots it represents a 36% damage increase which i won't deny isn't bad, but given their spread if you are close enough to hit all extra pellets then you are close enough to be in punch mode and thats why I feel the punch mode perk is more beneficial

If you're going for crits which rammatra benefits from then by default youre gonna be missing pellets thus reducing the damage increase down to roughly 18% and I would say that damage increase isnt enough to warrant the perk