260, that's what I'm trying to find out. I have an early RAR in 300 BLK. While the forearm is indeed a bit flimsy, it shoots very, very well. The flush fit-rotary mag has always functioned 100% too. I've read that the newer versions for the AR-A1 mag stocks have an ~improved forearm internal design. I'm curious if they did it to the flush-fit magazine versions.
I can't answer that directly for sure, but think the newer versions with flush fit mags are the same stock as the AI mags. These newer stocks all use a magazine well insert that you can change out for different mag types. I don't know about availability of different inserts, but in theory you can change an AI mag stock to use flush mags, and vise versa, so it stands to reason that these new versions probably have the same stock for both types.