By IN code cited, a rifle bought for handgun deer cartridge spec, converted to handgun..........would require NFA work.
And adding the buttstock would take it to rifle status, and require rifle cartridge spec.
...does the state now recognize an SBR in handgun form as a handgun, governed by handgun deer cartridge spec?
My guess is that the only reason the 16" line was added in this new HPR proposal was just some crazy redundancy defining a rifle. With both rifle and handgun regs matching if it passes, there is no reason to exclude SBR's, especially considering that they are currently legal.
If SBR can't run without buttstock for deer as handgun............then the build is pointless (no matter what the cartridge)
Still would be cool though.
Funny, I have a Super 16 TC bbl and can run my Contender as either rifle or handgun, by the change in grip/stock.
It however is in .35 Rem so works under either cartridge spec (trimmed for rifle use of course).