As I understand it, yes. Sometimes questions like this make me second guess myself.
I certainly hope so, because I have been.
To transport a pistol, you lock the pistol, put it in a case, and lock the case. Double locked.
An AR being restricted, is the same thing, lock the rifle, put it in a case and lock the case.
I almost always am shooting my AR when I go to the range, and often bring a pistol too.
Therefore, what I've been doing for the longest time, is locking my AR, and locking my pistol, putting them into the same rifle case, room permitting, and locking the case. My case is a hardshell, and I use 3 identically keyed padlock to secure it. No one at the range has ever called me on this.
It's common practice to lock multiple pistols in a single case, like those double pistol cases and what not. As long as the case is properly secured, as in you don't just have one lock on the rifle case and it can still be easily accessed, I don't see what difference it makes if there is a rifle in there with it too.
Meanwhile, some avid pistol shooters that bring several guns at a time to the range, will use a rifle case instead of several pistol cases.