It actually works out 20 Regiments - 1 from each hive - 5 Infantry, 5 Artillery, 5 Armoured and 5 Recon (that's how I am describing the Hellhound regiments). I stuck with the principle of keeping the different areas of the Guard separate.
The basis of my number crunching was this "With each hive housing between 10 to 100 billion people and 5 to 20 hives per planet" (Source:
http://warhammer40k.wikia.com/wiki/Hive_World). I decided to go for the maximum - 20 Hives of 100 Billion People each - in effect the whole planet had become a single huge hive. I have assumed 10% of the population under arms (even if not official pdf - I remember picking this % from a while back based on current day Earth - the stats from that show 10% of the population is armed forces (not technically true if you look at the statistics, as certain countries count their entire adult population as armed forces on the basis that they could be mobilised)). But ultimately it was a nice number to work with. Under the tithe of a hive world (which is usually set at the maximum level), 10% of the PDF (or the term I'm using 'men under arms') that equates to 1% of a hives population (20 billion across all the regiments and hives). When I worked out the numbers in my regiments, I realised that it didn't come close to that number (think I worked this out they would have to do 200 times this amount), that's where I came up with the logic that to fulfil their tithe, they paid the rest in equipment for other regiments. The reason I assume that they can pay their tithe in both manpower and equipment was that a single infantry squad is considered the same as a tank, despite there being fewer crew with the tank, therefor the equipment of the tank made up for the missing bodies.
Was that the number crunching you were referring too, or the size of a 'normal' regiment?
Oh, for my regiment, this is an annual raising, but slightly unusual in that all the hives are doing it at the same time - normally they would do it at different times, purely because of the logistics of transporting them all in one go
Automatically Appended Next Post: Oh, the similarities I was actually referring to in my first post was about the difference between the lower ranks and officers