From Halopedia, the Halo wiki
This glitch is most effective with scoped weapons like the sniper rifle and pistol, and is especially useful in multiplayer. After expending a full magazine from a sniper rifle or pistol, the animation is quite long, and in a Team Snipers gametype, the time spent reloading can make a huge difference. Rather than waiting, as soon as the new magazine is in the weapon, the player can press their press melee button/key. Instantly after doing so, one can press your scope button/key and immediately start firing, rather than waiting for the reload animation to finish.
This also works with scope-less weapons, notably the assault rifle, and can be used on Covenant weapons to reduce the overheat time. For these weapons, either a melee or rapid weapon switch to negate the remaining reload animations/overheat time. The weapon switch or melee must be timed according to when the new magazine first contacts the weapon, or approximately halfway through the overheat period. This might take longer than the regular reload animation rather than part of reload animation and the melee animation. Keep in mind that if the switch or melee is performed prematurely, the weapon-ready time will increase, or you will completely negate the reload and have to start anew.
To utilize a quick reload, a player presses the reload button, and while the magazine is inside the magazine case, melees quickly, stopping the reload animation (movement) and forcing the magazine directly inside the case. This trick also allows for the switching of weapons after the reload is finished.
Another method is also available, in which when the magazine enters the gun, quickly pressing Y, Y before the magazine enters the gun causes a faster reload than normal.
- Out of ammo and about to assassinate someone.
- In dire need of reloading.
This trick is hard to do with the following reloadable weapons:
- Shotgun (Possible, but it will take more time to reload if doing this after every shell reloaded. It is only viable after loading the last shell.)
- Needler (You do not exactly know when its crystalline “magazine” will enter its “chamber”.)
- SMG (By the time the magazine is in the gun, the reloading process is already done.)