On 20120829 I had to make a large detour to get from bm271 to 272. A shorter descent seemed impossible because of the steepness of the rock-hillside underneath bm271. But I was surprised to read that Iñaki Vigor and Carlos Sanz (see literature) did use a more direct (cairns-waymarked) trail. They also thought it was far too steep. But they found at the saddle between the two hilltops (between bm271 and the former bm271bis) a cairns-trail which took them without much problems to down below.
Also Javier et María-Jesús Sancho-Esnaola (see this previous post) took a short-cut but their starting point was the saddle east of bm297bis. They talk about following a cairns-trail, descending to the right down a gully (including some rock-scrambling), the route not always being obvious.
Conclusion: I have to return and check.