Yes, well many advanced modern artillery systems reached a precision similar to this. Trying to go any further and you bump into nasty problems such as wind turbulence and minute barrel bending caused by uneven sunlight heating. These problems are probably unsolvable in the near future so unguided artillery are basically stuck at under 1/400 precision.Regarding the accuracy of PCL-181/SH-15, I have seen a statement that 1/300 vertically and 1 mil horizontally. Under good weather conditions, it can reach 1/380 vertically and 0.5 mil horizontally.
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