Post 1986 at least, the ATF not only (heavily) regulates the sale and manufacture of any firearm capable of automatic fire, but they also approve all manufacturing plans to ensure that firearms on the market today are not easily convertible to full automatic.

If you get your hands on an old enough SKS, for example, a full auto conversion is dead simple (though obviously illegal without the $200 tax stamp), but for that very reason, those types of arms tend to get snatched up by the legitimate collectors and spirited away into collection vaults while their value climbs.

I'd guess it as unlikely that there are fully automatic firearms in use in crime of any significant amount, but that's only a guess, and not really based on anything other than my gut.

As far as political strategies go, I agree, in theory. As with all deeply held sentiments, in practice, it's harder to live and let live to those in opposition than just trying really hard... a fault I share with many.