Yesterday I finally looked at the rifle, and indeed, the 2 fore screws of the base were loose (???? )- (I swear I had them loctited). This morning I went to the stand and my 308 load, Vihtavuori N140 41,5 gr and Sierra 168 HPBT ( average of 2530 fps ), marked a group of .75" at 100 mts with the totally centered scope. The original Lapua match 185 gr ( 2420 fps ) made a group of 1,5" about 3 " lower and 1.5 " to the right without touching the scope. Thanks to all the ideas you all put forward.
regards from Spain,
Juan