So the hypothetical chain is:

Already-grandfathered PICA AR pistol
↓
Owner possesses a valid Type 03 C&R FFL
↓
Jensen assumption eliminates the applicable federal NFA approval/registration requirement
↓
Firearm becomes a shoulder-fired rifle while retaining <16" barrel
↓
Illinois §24-2(c)(7)(A) provides the C&R licensee exemption from §24-1(a)(7)
↓
Result: potentially lawful Illinois SBR possession

BUT: the entire theory ultimately turns on whether PICA considers that configuration change to be prohibited post-2023 manufacture of an assault weapon.

And there's a subtle point in your favor: PICA's endorsement itself is tied to the existing firearm's make/model/caliber/serial number, rather than creating a separate state “SBR registration.” That makes the argument that the grandfathered firearm remains the same firearm considerably more plausible.

So if I were ranking the legal issues:

Federal NFA: assuming Jensen applies → potentially no longer an obstacle.
Illinois SBR statute: C&R exception → unusually clear statutory exception.
PICA: the genuinely unresolved issue — whether the configuration change constitutes prohibited manufacture.

I would therefore characterize this as a plausible statutory pathway, not a confirmed legal pathway. Before anyone actually attempted the conversion, an Illinois attorney familiar with PICA would need to give an opinion on that third issue; the consequences of getting it wrong are substantial.

Originally Posted By AWDeity:
So everyone needs to get their C&R on point for this?

Originally Posted By StevieJ309:


In theory, yes. Although you would need to have a registered pistol to start with.

The crux of the issue though is, and I quote, "whether PICA considers that configuration change to be prohibited post-2023 manufacture of an assault weapon".  Doing this without a definitive answer is almost guaranteed to get someone hemmed up if caught.