NM gained or lost is based partly on a random factor, and partly (and majorly) on the value of units and leaders killed.
and why a random factor? . It should be based on the size of forces involved and casualties (its not the same a battle between 5000 soldiers than a major battle with 200.00.0 men in total).. and other factor could be if it is fought in an important area....
The other day I won a battle with longstreest inflitcting 21000 casualties to the union and i only had 3000... this should be an Austerlitz... and I didn´t won NM, this is ridicoulus... and in the same turn i lost a siege with a militia inside and i lost 1 NM because i lost that militia........
sincerely, something must be done with this, at least for the napoleonic game....