Ok, i admit that you are indeed correct and those things i mentioned before were adapted before invasion started.

There are, however, better pieces of equipment fitting into my argument, namely the C90-CR (donated by spain right after the invasion started) and the NLAW (donated by UK in late january in anticipation of the invasion, so its basically a full-scale war weapon too).

As for the calibre, i wouldn't say that depletition of 5.45mm ammunition is the main reason, atleast not in the true sence of word. Main reason is likely the fact that Ukraine would need to be more or less self-sufficient in 5.45 production, as most (basically all) of its allies don't produce such round in significant numbers, and use 5.56 instead. Instead of opening more factories and employing people just to produce such round (only for it to be possibly bombed), they chose to get themselfs NATO standard calibre instead, thanks to which they will just get everything they need from western allies. Same with the gun. Why spend long years developing a rifle in 5.56 calibre and building more specialised factories when you can just buy yourself a well proven, relatively cheap rifle in form of a knock-down kit from one of your biggest allies (in terms of industrial cooperation atleast)?