I'm confused by that last part. What do you mean by "Even if I wanted to go to the trouble to pin a 14" barrel to rifle length, such spare parts are not even available yet?"
I am trying to understand this because this is what I'm looking to do. If I buy a 14" Bren 2 MS and install the 922r kit, I can then pin/weld a proper length flash hider to get to 16"+ and then it's a compliant rifle, right? Can I use any flash hider?
Mine is an 11" barrel, which I like, especially in 7.62x39 since it only loses @ 100 fps at the muzzle compared to a 16" barrel.
It would be nice to have the ability to convert to a rifle using a spare 16" barrel (i.e.: in 6.5 Grendel), but no spare barrels, 16" or even 14", are available as spare parts from CZ, or any aftermarket vendor that I'm aware of.
Preferably you would blind pin a 2"+ muzzle device to your 14" barrel to get to the 16" requirement for a rifle with an actual butt stock, plus add a few other US-made parts to make it 922r compliant. Of course, nothing says you can't have a 16"+ barrel on a pistol, with or without a brace, and therefore, not have to bother with 922r.