The Raptor is a human version of a turian weapon developed for conflict on the low-gravity world Amar. Fighting at longer ranges than expected, the turians optimized a low-recoil, semi-automatic rifle with a scope, and issued it to their regular infantry, creating a hybrid weapon that was half-assault rifle and half-sniper weapon. Cerberus assigns the Raptor to Nemesis snipers.
The Raptor has a very low damage level for its class. This makes it nearly impossible to get one-shot kills, which is one of the key traits of many sniper rifles. Therefore, it is not suited for dispatching enemies one at a time like the M-92 Mantis or M-98 Widow.
On the other hand, low damage means that Raptor can be used against any enemy without being overkill (no need to decide whether it's worth spending precious ammunition to finish a weakened foe).
Reloading is very quick, even without reload cancelling. The Raptor plays like a more accurate M-96 Mattock with a built-in scope, more damage, and smaller clip size and ammo reserve.
The Raptor has a much lower power scope than other sniper rifles, which can actually make aiming and headshots easier, especially when switching targets quickly. This, combined with the incredibly fast rate of fire, makes it one of the most useful rifles in the game, especially for Infiltrators, who get free and unlimited time slowdown when zooming through the scope. It is actually possible to beat the game with only the Raptor and an SMG as a backup weapon (modded with Ultralight Materials, an SMG becomes nearly weightless), getting nearly +200% power recharge rate without sacrificing much firepower.
The rate of fire for this weapon is far superior to other sniper rifles, except for the M-90 Indra, giving the Raptor an edge in terms of putting shots down range. This can allow the Raptor to kill multiple enemies with surprising speed, or soften them up for more powerful weapons or squadmates.
Another admirable trait is its larger-than-average clip capacity, which allows the rifle to carry more ammunition than most sniper rifles.
Using Armor-Piercing Ammo and/or the sniper rifle penetration mod will greatly improve the damage output this weapon. An Infiltrator wielding a Raptor and utilising AP Ammo can take down a Harvester in a matter of seconds combined with Tactical Cloak.
When used by squad members, the Raptor is fired in three-round bursts just like the M-29 Incisor. This seems to be the squad member's method of shooting, however, and not a glitch, as they can occasionally be seen firing just one shot to finish off an enemy.
Consider upgrading the Raptor for the hands of Garrus or Ashley; Garrus' Armor-Piercing Ammo equipped on a fully upgraded Raptor can be devastating, but keep in mind his ammo can be obtained by Shepard and later upgraded at 50% effectiveness for squadmates, which is still nothing to be sniffed at, especially when combined with Ashley's Marksman ability.
For players who do not have the N7 Collector's Edition Pack, the Raptor is currently the highest theoretical DPS weapon in the game, though this is dependent on how fast the player can press the trigger button. The M-76 Revenant is a medium-close second for those who struggle with the Raptor.
The Raptor suffers a substantially lower damage penalty for firing without the scope than other sniper rifles, making it more useful to a sniper who is frequently on the move.
In the event of an unexpected close quarters situation, the player can "hip fire" the Raptor with surprising accuracy and effectiveness.