Ummmm, not reeeaaally.
Although this is a popular misconception used by flat earthers and the like to debunk the authority of the scientific method.
What is realized on occasion is that a known factor was not considered. These are the myriad of external factors you mention. ALL of which are known, just not always predictable.
That's because they lie within the body of understanding known as Physics. Apart for Higgs Boson and maybe Dark matter, we pretty much have physics sorted.
In fact, we have had this particular equation sorted since the first man (or woman) threw a rock at a mastodon. We've just been changing the variables since.
Once the bullet leaves the barrel there are exactly two and only two forces acting on that bullet. Friction and gravity. That's it.
In an experiment like this, we might say the coriolis effect?, nope, got that.
Wind? check, BC? check, MV? check, Altitude? check, BP? check, and so on.....
So the myriad of external factors are either differential wind/pressure calculations or the rate/amount of powder burn since we can be pretty sure the earth doesn't suddenly increase or decrease the speed of it's rotation and bullets don't pass through other dimensions where the laws of physics are turned upside down.
There is only one unknown here and that is how much wind and pressure will affect trajectory over that distance. Minor variations in muzzle velocity will have significant effects over distance but again, these are known but not necessarily predictable quantities.
AND they walked it in, which means they didn't even predict them, they built a tool that shoots a long way and shot it a bunch of times until they eventually hit something they were aiming at.
In my book it means literally nothing.
If, they had built the tool, done the calculations, and then ding!, hit the target at that distance on their first shot we could say WOW! And I would be impressed.
Instead, they dropped an apple off the Empire State Building and it did exactly what an apple dropped out of my hand will do which is hit the ground. Oooooooooooooh!!!
Actually, they dropped a whole bunch and eventually got one to fall into someone's open sunroof.
Total non event