Do note what I said: The ATACMS was developed in the 1980's. It has inertial guidance just as nearly all long range missile artillery systems have, even if it can be aided by GPS. All you need is specific coordinates of both the target and your position and some meteorological data. That's it. Even the Tochka missile that Ukraine has (or had) could hit something like a large ammo dump.

Do notice all the drone attacks done by Ukraine, btw. Far earlier Ukraine attacked Dyagilevo and Engels air bases and destroyed TU-22 Backfire and two TU-95 Bear aircraft. So that shows their capability.

Besides, Ammo dumps don't move, they can be only emptied, but that takes time. What is telling that neither side cannot hit moving targets deep inside in the other ones territory. I haven't seen one example of a moving train that has been attacked and destroyed (I may have just missed the occation). Russian aircraft don't dare to venture deep into Ukraine and attack trains and traffic.

The ATACMS was developed in the 1980's. It has inertial guidance just as nearly all long range missile artillery systems have, even if it can be aided by GPS. — ssu

You won't hit the broad side of a barn with just '80s INS, but the guidance modules have been updated over time to be able to correlate INS with systems other than GPS, since GPS is basically a relic of the past due to how easily it is jammed.

You won't hit the broad side of a barn with just '80s INS, — Tzeentch

Ammo dumps are far larger than a side of a barn. Or you mean top of a barn? Besides, as the solid fuel propellants of the missiles go old, old inventories aren't from the 1980's anymore. At least in the US.

We are talking of a 10-50m CEP with ATACMS. Does the job perfectly.

(Just for comparisons: 450m CEP for a SCUD B from the 60's, 4500m CEP for a V2 during WW2.)

We are talking of a 10-50m CEP with ATACMS. — ssu

With just a tiny, old INS over a 300km trajectory?

Yeah, no.

The whole point is for the GPS and INS to function together to reduce their respective errors.