The MP7 has a foreward grip, which a pistol cannot have without being an Any Other Weapon (AOW) unless its a machinegun.
Consider the HK MP5K -
A full auto MP5K with no buttstock and no vertical foregrip and a barrel of less than 16" is a machinegun.
A full auto MP5K with no buttstock and a vertical foregrip and a barrel of less than 16" is a machinegun.
A full auto MP5K with a buttstock and no vertical foregrip and a barrel of less than 16" is a machinegun.
A full auto MP5K with a buttstock and a vertical foregrip and a barrel of less than 16" is a machinegun.
A full auto MP5K with no buttstock and no vertical foregrip and a barrel of at least 16" is a machinegun.
A full auto MP5K with no buttstock and a vertical foregrip and a barrel of at least 16" is a machinegun.
A full auto MP5K with a buttstock and no vertical foregrip and a barrel of at least 16" is a machinegun.
A full auto MP5K with a buttstock and a vertical foregrip and a barrel of at least 16" is a machinegun.
Anything full auto is a machinegun regardless of barrel length or whether or not it has a buttstock or vertical foregrip. Being a machinegun "trumps" being a SBR or AOW, as it were.
A semi auto MP5K with no buttstock and no vertical foregrip and a barrel of less than 16" is a pistol. (This is an SP89, I think)
A semi auto MP5K with no buttstock and a vertical foregrip and a barrel of less than 16" is an Any Other Weapon (AOW).
A semi auto MP5K with a buttstock and no vertical foregrip and a barrel of less than 16" is a Short Barreled Rifle (SBR).
A semi auto MP5K with a buttstock and a vertical foregrip and a barrel of less than 16" is a Short Barreled Rifle (SBR).
A semi auto MP5K with no buttstock and no vertical foregrip and a barrel of at least 16" is a pistol.
A semi auto MP5K with no buttstock and a vertical foregrip and a barrel of at least 16" is an Any Other Weapon (AOW).
A semi auto MP5K with a buttstock and no vertical foregrip and a barrel of at least 16" is a Rifle.
A semi auto MP5K with a buttstock and a vertical foregrip and a barrel of at least 16" is a Rifle.
A rifle has to have a barrel of 16", but also has to have an overall length of at least 26." Probably none of these guns are 26" overall with the stock folded, but the 26" minimum length is measured with the stock at its
maximum length. A machinegun or SBR can have an overall length of less than 26."
Some of these combos probably don't exist, but if they did, and were importable (A whole 'nother issue) they would be the above - To the best of my knowledge.
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You can replace MP5K with MP7 in the examples above.
Therefore, the only non NFA MP7s would be -
A semi auto MP7 with no buttstock and no vertical foregrip and a barrel of less than 16" is a pistol.
A semi auto MP7 with no buttstock and no vertical foregrip and a barrel of at least 16" is a pistol.
A semi auto MP7 with a buttstock and no vertical foregrip and a barrel of at least 16" is a Rifle.
A semi auto MP7 with a buttstock and a vertical foregrip and a barrel of at least 16" is a Rifle.
The FN PS90 differs from the P90 in that it has a 16" barrel and is semi auto. The law makes no distinction between the weak hand hold area because it does not "protrude conspicuously" and isn't a vertical foregrip.
Its all confusing as all hell.
Basically, ATF = WTF.