Heavy guns (Assault Rifles, Sniper Rifles, LMGs) have massive reload costs. Rapid Reloader is often essential to reach the "50 AP" mark for a reload on an LMG.
The verdict on Rapid Reloader depends entirely on your weapon of choice:
"Rapid Reloader" is a perfect example of why Underrail is beloved by fans of complex RPGs. It isn't about flashy explosions or cinematic kills. It is about math, resource management, and optimization. It rewards the player who looks at a spreadsheet of AP costs and finds a way to turn the leftovers into a lethal advantage.