First, there are actually proportionally fewer firearms in Switzerland than the US. The proportion of handguns is even smaller. The total Swiss military/police force isn't actually that large. Roughly between 1 in 6 and 1 in 8. Second, service members have the option of keeping their weapons. Many chose not to. Weapons kept after demobilizing have the full auto function removed. Which, by definition, converts the assault-rifle to a plain semi-auto rifle. The main issues in both the US and Switzerland are with handguns. Outside Mexico, which in effect has no controls, rifles are not a major issue.
It also has to be noted that the Swiss gun laws are actually far stricter than US laws in terms of licensing, registration, allowed amounts of firearms and ammunition, and restrictions on how firearms are transported and stored.
If anyone wishes to institute Swiss legal controls they are going to have to fight it out with the NRA to tighten the laws and controls. Until that time I fail to see how Switzerland is an example of less gun control.