The High Caliber Rounds perk is very strong in Crucible, as evidenced by the overwhelming use of MIDA Multi-Tools and Uriel's Gifts. The advantage they offer is so strong that it should come with a trade-off in the form of a range penalty (or other penalty the balance team deems appropriate). It should not give added range as it currently does.
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A higher caliber round has more mass meaning it has enough kinetic energy to be lethal at a further range. Provided the ballistic coefficient remains the same, which mostly goes up with caliber.