但不论细节如何，这种“用进废退”的情形显然确凿无疑。

Regardless of the details, though, this would appear to be a clear case of "use it or lose it".

youdao

另外，因为无托步枪退壳口非常接近使用者的面部，当废弹壳跳出时使用者感到非常大的声音、气浪和烟尘。

Additionally, because the ejection port on the bullpup rifle is very close to the user's face, the user would feel greater sound, blast and smoke effects when spent casings eject.

youdao

语言学习的根本法则就是“用进废退”。

One fundamental rule of language learning is: "Use it, or lose it. ""

youdao