Other than materials and manufacturing methods, firearms have evolved very little for well over 100 years. Almost every one you can name uses operating principles or mechanisms developed around the late nineteenth and early 20th centuries.
Pretty much the same goes for automobile engines even though alternative technologies have existed for just as long or even longer (including electric motors). The main reason is that so-called "fossil fuels" have been cheap for so long, and now the main reason other technologies are finally being seriously developed is--guess what--the rising cost of dug-up fuel (and other things like environmental concerns); otherwise the internal-combustion-powered automobile would probably stay more or less the same for another few hundred years because it works.
A FAR better way of improving on current weapons IMO would be to improve projectile design with high-tech materials, and boost propellent performance with new chemicals:
Your suggestions would still just be refinements of existing concepts, namely putting bits of dense materials into people and things at high velocity using explosives. This doesn't contradict anything you've said by any means--I'm just emphasizing the fact.
Another way to look at this whole topic is that human beings happened to discover one of the best ways to inflict serious damage on one another at a decent range early on. We got a head start by the accidental discovery of chemical reactions that we really didn't understand until much later, and as a consequence personal weapons reached an early pinnacle in terms of development, which is why they haven't changed much in a while. Bear in mind that a lot of things are the way they are because of happenstance, which can and often does include the way the Universe happens to work in conjunction with the limits of our scientific knowledge regarding the aspects of physics that happen to be relevant to a particular application.
I imagine something like a 'smart' plastic which could be used as a bullet core, allowing a bullet to expand far more than possible with lead and copper, and expand at the appropriate time, after achieving good penetration. This would allow smaller and lighter bullets to achieve far larger wound channels than conventional bullets of the same diameter, while still reaching adequate penetration - Less recoil for the same would cavity volume.
Errr...creating larger wound channels requires greater energy and/or momentum, which smaller and lighter bullets have a harder time doing, no matter how fancy they may be. You could make them faster to compensate, but then they'd dump more energy into a minor temporary stretch cavity, making them less efficient. Precisely controlling expansion can have its advantages, but if taken to the extreme, the wound channel would be quite narrow for much of its length, which would mean a smaller overall wound channel.
Powders could be tailored to achieve delayed, or profiled expansion with new chemicals - allowing more gas volume, and higher velocity, for the same chamber pressures. Imagine a two-part powder that burns at a conventional rate until the bullet has jumped a few inches, and then flares producing a large volume of gas - the pressure would be abated by the additional volume.
That's how many hot loads are made today, but for the most part simpler, cheaper, conventional loads get the job done just fine. I'm not against progress, mind you, but practicality is usually the best way to go, and cost will always be an issue.
The primary reason for a lack of travel is the massive expense.
Expense has always had the capability of making things impractical, and the reason for the massive expense in the case of space travel is the energy problem. The only usable technology we currently have is chemical rockets, and that's a huge limitation due to its impact on cost if nothing else.
The moon mission and related expenses were justified, during the Cold War. Much of the same technology was applied to ICBMs, so every advancement in going to the moon was in fact a part of the arms race. It was essentially a program that helped to perfect ICBMs, but because it was interesting and captured the imagination of the nation, the public supported the massive required cost to go to the moon.
I don't want to go too deeply off-topic just for an analogy, so I'll keep it brief. What I had in mind was not just travel within the Solar System but interstellar and intergalactic travel, both of which are currently impractical for many fundamental reasons. We've hit a scientific and technological "brick wall" there that no amount of money alone could overcome (it will take time and massive intellectual effort, assuming that the human mind is capable of discovering what is needed and that there are usable things to discover in the first place).
But space travel anywhere in the galaxy has been entirely feasible for awhile.
Galaxy?!
If we could do that in any feasible, practical sense, then believe me, we already would have without hesitation. But in case you hadn't noticed, interstellar space is VAST--the Milky Way alone is approximately 100,000 light-years across, and light, in terms of our common experience, is pretty fast.
It may be off-topic, but I'd really like to see how you'd attempt to justify such a wildly fantastic claim.
Because of the law primarily.
Since civilians do not have widespread access to full auto and similar concepts the speed of progress to new technology has been limited.
This concerns refinements of existing technologies, but regarding truly novel and different technologies (i.e. something other than exploding chemicals and kinetic projectiles), there is still that nagging energy problem to contend with.
100 years ago the field was wide open to invention.
True, but it didn't take long to come up with designs that are still practical today, especially since a particularly gifted inventor (or three) just happened to be working on firearms at the time, as well.
In the civilian economy technology can stay alive and grow. Someone can sell a few hundred here, some thousands there. Improve it some more years later. Sell a few thousand more.
But that environment no longer exists for most cutting edge technology in firearms because of legal restrictions.
Firearms development could still never come anywhere close to electronics--which most people have in mind when thinking about "technology"--with regard to speed and potential because there is such a mother lode of scientific knowledge (they're even using quantum mechanics in processor designs these days) to be mined for the latter while the former is physically constrained. Even with no legal restrictions whatsoever, I do not think, in analogy, that it would be possible to double the destructiveness of a firearm every year without increasing recoil and the size of the firearm and its ammo--no such technology could be quickly developed as so little relevant scientific knowledge exists (i.e. that mine has been tapped out). And while the following may be a "dangerous" statement to make because one never quite knows when a major scientific breakthrough may occur, perhaps there isn't as much that can potentially be done simply because the Universe says so.
To put things in perspective, someday we'll approach the limits of what we can do with information technology--which is still in its infancy, relatively speaking--as well, and people will wonder why electronic gadgets aren't being developed as rapidly as warp drives, for example.
Right now, we happen to be living at a time when electronics can and are being developed quickly, and many of us unrealistically expect that everything else could be developed just as quickly if we only tried hard enough, but in reality that is not the case.
