Why the confusing non standard ammo calibers?

[intensity]

Anyone else confused by this? When I see "9mm" or "7.62" specific size rounds come into mind. It appears that's not the way it works in Underrail and we have a linear progression starting from 5mm all the way to 12.7mm which while being a strange way to categorise rounds it's not false but there are many different varieties of bullets that are under such broad categories.  However, suddenly we have .44 ammo that throws that into disrepute.

It seems that ammo is just categorised generally because obviously the ammo is totally different if used in rifles vs handguns, most specifically the difference is noted with 9mm. Still doesn't explain why .44 is exempt.

The existance of unique guns like the K&H 9mm (obviously mp5 9mm) also adds confuses me.

AFAIK:

5mm = .22
7.62mm = 30-30 or a number of 7.62x51 nato or russian variant
8.6mm = .338 magnum
9mm .357 magnum for pistols, .35 winchester or other variant
12.7mm = 12.7

[Hazard]

As far as I understand, Underrail takes place in quite a distant future so .44 is probably just .44 Magnum or some futuristic derivative (being pistol only), and the rest are universal one-cartridge-fits-all things that magically due to hundreds of years of firearm development can change their ballistic properties depending on barrel length. It's kinda pointless trying to match them to real world cartridges, even though they're clearly based on them: after all it's an RPG without much focus on particularly realistic weaponry.

[kasper747]

I can feel your point, but I dont understand what you are talking about. Probably you more are to pro in weapons. Could you explain in detail what you are speaking about? From my perspective the calibers seems to be legit, as i know 9mm and 7.62 do exist.

[intensity]

I can feel your point, but I dont understand what you are talking about. Probably you more are to pro in weapons. Could you explain in detail what you are speaking about? From my perspective the calibers seems to be legit, as i know 9mm and 7.62 do exist.

The game has linear progression of calibers starting 5mm being the weakest to 12.7mm being the strongest. But it makes no sense in real life and ends up being counter intuitive for me. Especially with odd things like a weak 9mm SMG which is probably only an easter egg and the .44 magnum which no longer uses millimeters.

Take for instance 7.62mm, one of the most common rifle cartriges, vs 9mm. In underrail, 9mm is considered the stronger bullet. See this picture for ref http://www.prep-blog.com/wp-content/uploads/2013/01/22lr-9mm-556.jpg

Do you see what I mean?

The absence of .45 also baffles me.