There are historic turn -bolt action conversions to fully automatic (EWnfields for instance in both World Wars) and more common there have been some straight pull bolt action rifle conversions before WWI and it is very possible and IMO would be rather easy to turn other straight pull bolt actions into full auto. There has even been a full auto muzzloader in the past. But yes any semi auto can be converted to full auto, but it is not always so easy and for the AR15 yes it can easily be converted to full auto (not all models though) with a "drop in sear", but those sears have been illegal to make for civillian ownership since 1986 and they are serial numbered, registered and taxed at $200 each. You can buy a good one for about $3,000 to $5,000. There is a type of cheaply made way to convert most ARs to full auto but they are stil a few thousand dollars a piece and need a lot of fine tuning and are not reliable. But back to the point, ANY gun can be made full auto including muzzloaders, but it is much easier to make a full auto from scratch cheaply and it is much easier to make than a semi auto actually. You can make it from scarap metal or from hardware store parts so the purpose of banning any semi-auto is moot since it is so easy for criminals or nutjobs to make one of these... http://thehomegunsmith.com/ And that is not the only design out there. There are plenty of videos of people making full auto guns from hardware store parts out there.
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