OK , lets put the question in another way .
Of which caliber should be the standard rifle issued to the common indian soldier ??
That is good one, as standard rifles means that it should be able to shoot accurately and consistantly at a range at which humans are capable of targeting the enemy in human form. That is generally between 300 and 400 meters. One should be able to engage enemy human figures between 300 to 100 meters with single , burst and automatic deliberately aimed and semi aimed fired shots / bursts.
The weapon should be able to produce very heavy volume / rate of accurate and constant automatic fire to engage enemy quickly at close ranges less than 50 meters range with as little dispersal as possible.
The stopping power of the ammunition should kill/ incapacitate the target and not merely injure. The aim of the ammunition must be to render the target resistance less rather than to merely penetrate and injure.
The weapon should fire ammunition with sufficient stopping power to pierce protected or semi protected human being to kill or incapacitate him at ranges 500 meters and less.
The mechanism should be simple, rugged and user friendly demanding minimum maintenance.
The ammunition should have accuracy and consistency, economical and should not harm the firer including in its toxicity. It should produce less smoke, heat and flash.
Ammunition should be light and shorter in shape with good ballistics and not designed for wounds and injuries considered inhuman. The ammunition should be lighter and in a shape to house larger number in a given magazine.
For a good assault rifle the ammunition should be adaptable in multi platforms and weapon systems and incorporate ballistic needs of differing ranges.
That broadly is the requirement. What fits the bill?