The way I see an ideal Swiss army would be a concentration on locally organized Guerilla forces anyway - heavy tanks and artillery could be completely canceled and the airforce could be reduced to a pure air police. In a hypothetical war against a big nation, air superiority would be lost in probably less than a day, which immediately renders stationary forces and tanks useless - but the biggest asset we would have is precisely those bunkers and 500k rifles in the hands of people that are well enough trained at distance shooting. All that would be needed is a difficult-to-suppress way of communication. For that matter I'd issue a new kind of radio device to all households and include it in a new law. Let these radios create an encrypted ad-hoc network with frequency hopping and lots of random noise on unused channels. Make the software and hardware Open Source and cheap, such that a) they can be improved by the community and b) can be used by oppressed people in other parts of the world. Then we could wish any future agressive foreign government much fun at financing a long drawn out oppressive war against a mountainous country with 8M bunkers, 4M radios and 0.5M rifles - with all useful bridges and tunnels gone ;-).
I'm impressed that there's lots of > 300m training, 400m effective range is achievable with this class of rounds, but the bullet drop after 300m is serious. But you wouldn't want an enemy to get complacent if they were > 300m from your people.
Not sure about your ideal; the heavy forces have a deterrent effect, they ensure reducing them in an all out war would be expensive. As I recall, the German General Staff figured taking Switzerland during WWII would break 85 divisions, a cost they simply couldn't afford. Which came at a cost to the Swiss, you mobilized your army, shut down your stock market, etc., the defensive "threat" was credible, deterrence was achieved. (I haven't read it yet, but this is supposed to be the current best book in English on the topic, written by a very solid and trustworthy author: http://www.amazon.com/Target-Switzerland-Swiss-Armed-Neutral... ).
It's also worth noting the accepted costs of the Swiss strategic system, then, during the Cold War, and presumably during a future attack by a major nation (which, as it became more likely, you might presume would include Switzerland bulking up its heavy forces in response).
Very bloody minded: give the indefensible lowland big cities to the enemy (where per the book I linked to previously, the citizens practice "Total Resistance" using among other things those decommissioned from military service older rifles), and retreat to the mountainous country and make the enemy pay for every foot they gain, with little more than bullets and rifle grenades if need be. Per the apocryphal quote from the Imperial Japanese Navy admiral who planned the Pearl Harbor attack, "a rifle behind every blade of grass".
Also, after the Vidkun Quisling debacle, a general order that henceforth no surrender order would be legitimate, and to fight to the last man and foot of ground. (Well, meter of ground of course.) Credible deterrence, which I submit to you, your current heavy stuff aids. Certainly aids in deterring any less than all out attempt to "punish" Switzerland for whatever. Right now the latter is "unthinkable" in part because you've got those heavy forces.
The size is a tricky question. Don't know about the interior ballistics of your Gw Pat 90 bullet, although Wikipedia says it's properly "designed for terminal ballistic instability".
This is very important, because as discovered by Martin Fackler in the '80s, 5.56x45mm Full Metal Jacket (FMJ) ammo as fielded by the US is terrible at producing field disabling wounds unless, when it tumbles (as all bullets do when changing media from air to whatever), it ideally does so at a high enough velocity for it to break at the cannelure (the crimp in the jacket that helps hold everything together), and ideally the back portion then fragments. Otherwise it does little more than poke a pencil hole through a human, with a flip to exiting rear ended (which by itself, per Fackler's research, tends to do little damage, as does the high velocity shock waves), and of course this assumes bone isn't significantly hit etc.
In practice, we, the US, have seen it isn't a very effective cartridge, and that's not a surprise given how it was forced on the US Army (an action which wasn't, BTW, inherently incorrect, for that part of the Army was very corrupt).
The rule of thumb is that for every inch you chop off the barrel, you lose 50 yards/46 meters of effectiveness. So those who care about this, like the US Marines, still use 20 inch barrels, the M16 vs. the M4 carbine at 14.5 inches.
And strangely enough, so follows the SG 55x models, per Wikipedia:
And you're correct, if you're doing pure assault stuff, short range action, chopping the barrel to 551 or 552/3 length can get the job done. But as we've found in e.g. Afghanistan, 551/M4 length is disastrous if you have to "reach out and touch someone".And thanks for all the "on the ground" information you've provided about the current situation over there.