On the two Express' here at casa del 9mm, I have swapped to barrels with the detent. One of these currently runs a factory extension as well.
The other has used, on occasion, a new-style 26" VR Express barrel that I bought new. It is my only rem-choke barrel and I bought it so I'd have a barrel long enough to go shoot with Dave McC someday. His club has a barrel length restriction. Now I have a 30" fixed choke VR that is way nicer.....
Anyway, this new Express barrel does not have the detent or even the hole to install one and the mag cap comes loose all the time while shooting. If I install with pliers, it will stay put but who wants to do that?
Mike