No, they're prohibited from import, the CQB is an NFA weapon because of the barrel length, other models are not suitable for "sporting purposes" as defined in 18 USC 925(d)(3).
In theory you can take all but the CQB into the US on a Form 6NIA temporarily as they're not considered imported so the sporting purpose test does not apply.
However the ####wits at the Import Branch can't tell the difference between the FA and SA receivers so they keep rejecting my applications saying they incorporate the frame or receiver of a MG.
Eventually someone at the Technology Branch will sort it out but don't hold your breath. I've been waiting for ages for a ruling.