I think you meant to say, if it had been a rifle. AR-15's don't posses special properties... anything shooting a .223 or 5.56 round will have similar properties.
The damage truly depends on the type of ammunition used (as well as caliber). FMJ (Full Metal Jacket) ammunition, what seems to be described in the article you referenced, is a non-expanding type of ammunition, typically causing less destruction than expanding types such as HP (Hallow Point), which flatten and expand on impact.
Muzzle velocities from a rifle are significantly higher than handguns, which does translate into more kinetic energy. The additional energies in a rifle cartridge will cause more shock damage to organs, as described in the article, however.
HP ammunition (not commonly used in rifles) is designed to be devastatingly lethal - specifically designed to leave very large wounds in the target, which have little hope of closing/repairing the wound.
To add one other note, HP ammo has the additional (generally beneficial) property of penetrating significantly less than something like FMJ. Through its design it imparts the bulk of its kinetic energy on the first obstacle it hits, which greatly reduces the chances of it doing damage to something unintended.
The damage truly depends on the type of ammunition used (as well as caliber). FMJ (Full Metal Jacket) ammunition, what seems to be described in the article you referenced, is a non-expanding type of ammunition, typically causing less destruction than expanding types such as HP (Hallow Point), which flatten and expand on impact.
Muzzle velocities from a rifle are significantly higher than handguns, which does translate into more kinetic energy. The additional energies in a rifle cartridge will cause more shock damage to organs, as described in the article, however.
HP ammunition (not commonly used in rifles) is designed to be devastatingly lethal - specifically designed to leave very large wounds in the target, which have little hope of closing/repairing the wound.