Man how I wish they didn't have the once a rifle rule.
Handguns, other than muzzleloading, must have a barrel at least 4 inches long and must fire a bullet of .243-inch diameter or larger. The handgun cartridge case, without the bullet, must be at least 1.16 inches long. Full metal-jacketed bullets are not permitted.
If it started life as a pistol, it can be swapped back and forth between rifle and pistol configurations. If it started as a rifle, it must stay a rifle.
So, if you buy a stripped AR-15 lower, its first configuration is critical.
How about just building a 300 aac off this lower, http://megaarms.com/ar-15/lower-receivers/forged-lower/
Just be sure its M0210 ( marked as a pistol lower) The 300 BLKOUT makes the case and bullet diameter.
At the risk of sounding shady, it isn't that critical, because you and whomever you tell are the only ones that would know the true original configuration. And technically, you could install a pistol buffer and short upper for two seconds and the original configuration is now magically pistol. It is an asinine rule.
The 4473 would show whether it started life as a pistol, rifle, or other. Of course the ATF is pretty much the only agency that would check the 4473, but that doesnt make it any less illegal.
Dumb, dumb, dumb laws.
If I understand you correctly, you are meaning taking a 10" short barrel upper, welding a 6" can on to it so the length become 16", then yes, it is a rifle length and would only need the tax stamp on the suppressor, not the SBR
an AR pistol can have a 30" barrel if you want it to...just no buttstock and no foregrip
Incorrect.
See below text for Indiana regulations:
IC 35-47-1-6
"Handgun"
Sec. 6. "Handgun" means any firearm:
(1) designed or adapted so as to be aimed and fired from one (1) hand, regardless of barrel length; or
(2) any firearm with:
(A) a barrel less than sixteen (16) inches in length; or
(B) an overall length of less than twenty-six (26) inches.
As added by P.L.311-1983, SEC.32.