Larger rounds require much larger supply stores and logistics to work with. That's why the M16 uses 5.56 instead of 7mm, and that's why they designed the MP-5 to use pistol rounds. This is on Earth, now imagine if you had severe restrictions on mass and infrastructure....
Doubtless they'd bring shell catchers and re-load used shells instead of bringing every round. Just a minor descriptive detail.
Conversely, you'll end up needing larger supplies of lower-calibre rounds, if they are a good deal less effective.
The 7.62 mm NATO round would probably easily deal with any forseeable dangerous organisms. A 12.7mm would make short work of an organism the size of Amphicoelias, though it's possible that multiple 7.62mm rounds could take down such a large animal over a more prolonged period.
Generally the bigger an animal gets, the lighter it'll have to be (by pneumatising its bones for example, as with large dinosaurs) to support itself. Of course, on a planet with lower gravity, organisms can be larger, but they could generally be more gracile as well.
12.7mm would probably be the largest calibre you'd realistically need to use on a wilderness planet. A 12.7mm explosive round with fusing, etc, would however likely be able to have only a small explosive payload. I have, however, seen some interesting concepts for 12.7mm rounds with small amounts of explosive payload.
Producing ammo would be difficult though. It's a toss up between bringing no rounds or guns but the means to produce them on-site, or bring some weapons and repurpose other machinery if necessary, and also a toss up between bringing/making semi-auto weapons in a light
and heavy calibre, or bringing a light calibre only, but also having small quantities/the ability to produce small quantities of fully automatic weapons, that have you risk shooting away all your ammunition.
Guns themselves should be easy enough to produce, given a simplified enough design (AK was meant to be built in any machine shop, if you're seriously planning on colonising a wilderness planet, you better have a pretty impressive machine shop), but ammunition would be more difficult. You're talking propellants, primers, forming projectiles... drawing cases... all of which needs pretty intrinsic infrastructure.
...And can therefore conclude that manned interstelar travel is a total pipe dream unless we find a way to do it utterly different
Not "utterly different". A wright flyer and an SR-71 work on
vaguely similar principles and have a lot of
vague similarities. It's just that the wright flyer doesn't contain any of the highly advanced technology (advanced jet propulsion, titanium alloys, hydraulics, instrumentation) that the SR-71 has.
An interstellar spacecraft and an interplanetary (we've only really done LEO up to now, it's
vaguely similar enough to interplanetary space to give us a lot of good experience) are vaguely similar in difference, to the Wright Flyer/SR-71. Those two examples are both aircraft, one is just more advanced than the other. These two examples are both spacecraft, and the same things apply (though obviously at different scales here).
The biggest problem is probably propulsion, because we need really high exhaust energies and energy densities and stuff like that for interstellar spaceflight to be viable. The other is probably all the stuff related to the crew and actually keeping the ship running. That's a whole other story. :dry:
I just performed the calculations for the rocket and it came out to be so high that for the first time in my life i actually felt hopeless...
Could you explain in a coherent manner what calculations you did and how badly they came out? What parameters did you use?
