On paper, certainly.

But a lot of those missiles have been stored somewhere in Siberia for 40+ years. Their condition is probably less than stellar. Who would regularly inspect and maintain random ammo dumps located five timezones away from Moscow in the middle of nowhere?

I suspect that at least some of those missiles are outright out of commission and others are unstable enough to be a danger to the Russians themselves.

Also, see this anti-aircraft gun in action: https://www.youtube.com/watch?v=6IwqmezeSuQ

Maybe but those are big assumptions. Does the USA inspect it's missiles in the middle of nowhere?

IDK, but that is hardly relevant to the current situation. We aren't trying to one-up each other in a "who is worse" rhetoric content, but looking at the situation at the Russo-Ukrainian front.

From what I get, Western stuff delivered to the Ukrainians is in working order, while the Russians shells seem to have a fairly high percentage of duds - usually an indicator of a fuse degraded by long and inadequate storage.

And if shells frequently fail, so will other long stored equipment.

It's exactly the same. Two global leaders in military power.

> Maybe but those are big assumptions. Does the USA inspect it's missiles in the middle of nowhere?

The US almost certainly does, but the Russians might not. They've been shown to have neglected routine maintenance in ways that caused very critical problems for their military (e.g. they lost a lot of expensive advanced vehicles, because their unmaintained knock-off tires disintegrated).

Both these videos are long, but they had a lot of interesting ideas and insight on this topic:

https://www.youtube.com/watch?v=i9i47sgi-V4 [specifically 33:10] (How Corruption Destroys Armies - Theft, Graft, and Russian failure in Ukraine)

https://www.youtube.com/watch?v=KJkmcNjh_bg (All Bling, no Basics - Why Ukraine has embarrassed the Russian Military)

They are already running out of Kalibr and Iskander missiles. Why would they started using S300 in Groun 2 Ground role?

https://www.thedrive.com/the-war-zone/russia-now-firing-s-30...

Any proofs?

First, there is no proof of the original claim, other than words of Ukrainian mayor.

Second, this explanation is much more logical than the version with russians firing superexpensive anti air weapons to random ground targets.

Third, there were photos of these missiles, and they belong to older series of rockets. Russia dismissed these old s-300 long ago, but Ukraine have plenty of them.