Yes - the BA is 19mm set up for the BA rings you have whereas the BB is 17mm. You have a very nice set of RALS.4 rings so the best bet is to change the bases. Would be your least expensive option. Ron
PS I see the number 20 stamped on the rear of the front base and 21 on the rear.....definitely for early 17mm base rings. I've got both so if you need a measurement let me know.