C-Rating

Multiplying a pack's C-rating by its mAh capacity gives its maximum continuous discharge current in amps: a 1300mAh pack rated 20C can supply roughly 26A continuously. A high-torque motor under a heavy spring draws real current spikes on every shot, and a low-C pack can't keep up, showing up as sluggish cycling or voltage sag rather than an outright failure.

Manufacturers' printed C-ratings are also notoriously optimistic marketing numbers more often than lab-verified figures, so experienced buyers tend to favour reputable brands and slightly oversized capacity over trusting the number at face value.

A quick sanity check some players use: if a gun runs noticeably better on a fresh, name-brand battery than a generic one with an identical printed C-rating, the printed number on the cheaper pack was probably optimistic.