ACR stock along with Bren adapter is a great setup!
As a ACR owner I have always loved the ACR stock so it was a no-brainer for me to add to my Bren
The Bushmaster ACR™ Enhanced 7-Position Telescoping Side Folding Stock is made of high-impact composite polymer with a rubber butt pad. The seven position telescoping stock has an adjustable length of pull from 11" to 14" (when installed on an ACR). The stock also unlocks and folds to the right side and is held open by a hinge detent, allowing for the rifle to become more compact but still able to be fired. An adjustable, locking cheek weld piece can raise 1/2" for better sight alignment with optics. A sling can be attached to the integral webbing loop, to a quick detach coupler that can swap to either side or to the single point sling loop.