“...I thought fully automatic rifles were banned ... he capacity to switch between semiautomatic and fully automatic ... If such a definition is to be found in the ATF site I could not find it in any direct fashion-’
“Assault rifle” has been a piece of military nomenclature, not a legal definition.
BATFE (supposedly) bases its rules on legislation like the National Firearms Act and later laws. “Assault rifle” does not appear in any of their documentation (”Assault weapon” has no definition of any sort - PR nonsense dreamt up by the anti-gun folks to confuse the ignorant. Maddeningly, it’s caught on).
Hiram Stevens Maxim himself began the uncertainty by calling his invention the “Automatic Gun” or similar names ... it operated itself - fired, extracted, ejected, fed rounds under its own power unlike hand-operated guns of those times like Gatling, Gardner, Nordenfeldt and others.
A semi-automatic firearm discharges one shot for each pull of the trigger and thus does not fall under this aspect of BATFE jurisdiction.
The gun industry itself added to the confusion by using the word “automatic” to punch up marketing of semi-auto pistols 125 years ago - referring to newfangled handguns that reloaded their chamber without any help from the user, “automatically,” after each trigger pull. “Colt’s Automatic Pistol” wasn’t just a trade name, it became a byword and a proverb, through which Colt dominated the market for 50 years and more. Easier to say “automatic” than “self-loading” or “semiautomatic”; cheaper to roll-mark it on each pistol. (It did help, that they acquired great designs and turned out products of superior quality)
Fully automatic firearms discharge two or more shots for each pull of the trigger. That is the legal definition BATFE uses. Any such firearm is legally a “machine gun”: possession and transfer are thus regulated by the agency.