[aidenn0]

Clearly the barrel-length restrictions were intended to be about how easy they are to conceal. There was an attempt to draw a distinction between long-guns and hand-guns.

The NFA ended up exempting pistols, which results in the strange situation where manufacturing a pistol to fire a .223 Remmington is legal, but shortening an AR-15 is not.

Perhaps if they only exempted revolvers it would make more sense.

[sidewndr46]

That is false. The objective was to prevent the handgun ban from being circumvented. The handgun ban never became law but we're left with an oddball restriction around short barrels on rifles.