It was legal before. Now, with a post 8/1 FCU? … maybe?
“(b) a semiautomatic pistol with the capacity to accept a detachable feeding device and includes at least 2 of the following features: (i) the capacity to accept a feeding device that attaches to the pistol outside of the pistol grip; (ii) a second handgrip or a protruding grip that can be held by the non-trigger hand; (iii) a threaded barrel capable of accepting a flash suppressor, forward handgrip or silencer; or (iv) a shroud that encircles either all or part of the barrel designed to shield the bearer’s hand from heat, excluding a slide that encloses the barrel.”
The forward magazine holder is absolutely a “protruding grip” that can be held by the non trigger hand. It’s not a vertical foregrip according to the ATF and therefore doesn’t become an AOW. But from the state law perspective, yeah that’s one bad feature.
Second is that forward mag holder technically meets the wording of feature (i). It is capable of accepting a feeding device outside the pistol grip. Now, it can’t feed from that location, but the magazine is indeed a feeding device and it is attached outside of the pistol grip. It doesn’t meet the INTENT of the description of the feature, but it does meet the wording.
I totally understand people who have a looser interpretation of the feature (i). That’s why it’s a “maybe”. Unless you hav a threaded barrel, then that’s definitely a no-go.