Why Sentinel prime did not use his cosmic rust gun again ?

Why Sentinel prime did not use his cosmic rust gun again ?

Can MCU Thanos take a punch from Optimus Prime? - Quora

static.wikia.nocookie.net/villains/images/9/95/Sen

In Hand Images for Transformers Studio Series Sentinel Prime

Transformers: Cosmic Rust, Explained

Transformers Details That you Missed !, PART 10

Heavy/Scratch: - DIY Cosmic Rust Gun & Studio Series Sentinel

Sentinel Prime vs Optimus Prime (AOE) - Battles - Comic Vine

Sentinel Prime (ROTF) - Transformers Wiki

26 minutes Video of Transformers Details that you Surely missed

This is how Sentinel Prime betrayed the Autobots from the start

Transformers Did You know ?