u/DiemCarpePine

This weekend Xur is selling Speleologist with Envious Assassin.

It is the only Rapid-Fire Frame machine gun that can get Envious Assassin. EA increases the magazine up to an additional 200% if you swap to the gun after getting kills with another gun. This includes things like mag options and the backup mag mod. Rapid-Fire frames have the largest base magazine sizes.

On the roll that Xur has, you can get up to 282 rounds in the magazine, which will let you hold down the trigger for around 20 seconds without reloading. This isn't incredibly useful or powerful, but it is very very satisfying and fun.

But wait, there's more.

Speleologist is also craftable. So, if you have the pattern or have harmonizers to burn, you can craft it with Extended Mag as well. This pushes the full mag size to 342 rounds. Pair this with Adagio to slow down the rate of fire, and you can hold the trigger for around 25 seconds without reloading.

If you go all in on this, and throw in Actium War Rig for passive reload, you can fire uninterrupted for about 45 seconds. Here is a video of a full mag dump at 342 rounds with Actium.

Again, not a meta gun or anything, but if you enjoy shooting an endless stream of bullets at the hordes, it cannot be beat.