It might just be my personal opinion, but I feel that Magnums might be too good at almost everything. They excel at mid range skirmishing. They are reliable, accurate, and mobile, and are superior to the miniguns, machine guns, pistol, and rifles in most cases. They are also effective at close range because of the large and reliable burst damage each shot deals. In addition, they hit and kill targets at long range about as reliably or more reliably than the rifle, because the sum of the aimed shots are about as accurate and Magnum shots are more likely to penetrate armour.
I'm not even mentioning that the Magnum is a one-handed weapon light enough to be carried by the weakest soldiers. When a month of time passes, the superiority of Magnums becomes even more pronounced. Tougher, more heavily armoured targets like the Men in Black Enforcers make lower damage weapons less useful and the armour penetration of the Magnum even better.
The magnum isn't game-bustingly overpowered, but many other options seem to pale in comparison.