Dear ATF, the intent is to fire it with just my arm, any shoulder contact is COMPLETELY coincidental...
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it's not illegal unless you completely "intend" to have it shoulder fired.
Capitalization in the following code is mine for emphasis. It can't be an SBR unless it is first a rifle. It can't be a rifle unless you "intend" it to be one. Arbitrary and capricious much?
"(7) The term ‘‘rifle’’ means a weapon designed or redesigned, made or remade, AND INTENDED to be fired from the shoulder and designed or rede- signed and made or remade to use the energy of an explosive to fire only a single projectile through a rifled bore for each single pull of the trigger.
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The term ‘‘short-barreled rifle’’ means a rifle having one or more barrels less than six- teen inches in length and any weapon made from a rifle (whether by alteration, modification, or otherwise) if such weapon, as modified, has an overall length of less than twenty-six inches."