The case is the same length as a 260 rem.
There were just older threads/posts on various boards complaining about the 2.9 COAL not fitting in AI style mags. I've done some digging but my eyes are almost hurting trying to find current threads/info on this and I wasn't sure if this was still an issue. For me, it would be an issue if I could not get these to feed out of a detachable mag box.