If you wanted numerous units with the same stats then the copy and paste facility could do that.
Yes, you can't then later change them.
The shallow structure is designed partly to make it harder for people to cheat when playing by email.
( And or online, if the game sells enough to justify that work. )
If this was a database driven design, yes you might see weapon as an entity.
Lee metford does xyz, allocate that to a unit linked by foreign key.
And yes, this would be a significant change to design.
You'd then have to build a table of weapons.
That would arguably move the work to be done from each unit to a huge list of muskets and rifles.
The main problem I would have with that is it's not a very realistic way to model battlefield combat.
Personal weapons do not define battlefield effect.
People do.
Mostly.
Support weapons are admittedly different but there are so many that building a profile for each would be way less useful.
Where do I get this idea from?
Numerous operational reseach studies all come to the same conclusion.
It's the men shooting the weapon that decide effect rather than the weapons they shoot.
Admittedly most of these are after our period, but it seems a bit unlikely that people totally changed between 1815 and 1945.
It's perhaps counter intuitive but studies of combat in afghanistan green zone and Iraq, ww1 and ww2... and napoleonic warfare.
These all come to similar conclusions and the effective range of a rifle or musket is oddly similar under battlefield conditions *.
The vast majority of decisive firefights happen under 50 yards range.
Above that range, the casualty rate drops dramatically.
If you ignored support weapons, you could pretty much set the range to 200 for everything and use the musket curve for moderns.
Opinions differ on exactly why, but 99% of riflemen perform in battle at well under 5% of their effectiveness on the rifle range.
They can't hit a person until that person is well under 100 yards distant.
If indeed they even try to.
Doesn't matter if the gun's theoretical range is 2000 yards or 200 yards.
Which is why the soviets decided automatic fire and a gun that wasn't particularly effective over 200 yards was just fine for them.
So a brown bess or french.. german... equivalent... whatever...
No discernable difference.
Brown bess vs m4 is not just down to rate of fire, because you also have to factor in the empty battlefield.
Infantry now creep and crawl around - since roughly 1900.
A much bigger difference is how many of that 1% you have in the unit.
That differs.
Elite units have way more of those guys, but often the same weapons and often rather different characteristics.
The difference in effective range will of course increase hugely when you compare rifles rather than smooth bore.
There again, "better" units reloaded faster and more reliably.
*
Note that there are exceptions to this.
Combat on particularly open terrain like the veldt using "new" weapons and tactics such as the Boer war.
Or just really awkward open terrain like the mountains of afghanistan which more recently led to calls for a larger calibre rifle.
Modern militaries will of course engage at longer ranges.
They talk much more about suppression and area denial than killing anyone though.
The aim being to pin, suppress and maneuver or call in fire.
If anyone is actually hit by such fire then this is a bonus.
The military usually define effective range at the point 50% of shots hit.
I'm not being quite so exact here in my usage.
And of course....
If you disagree with any or all of this then no problem, you can set whatever stats you prefer.