You can download now a BfX version capable of working with custom dragfunction. Read the gettingstarted workbook to understand how. As this is the most complex addition to BfX since its beginning, and although the software is full of checks, there is increased risk of crashes. Take care and save your work regulary.
The Lapua dragtables can be downloaded here: http://www.lapua.com/upload/ballistics/qtulapuaeditiondragtables.zip (http://www.lapua.com/upload/ballistics/qtulapuaeditiondragtables.zip) You can also download a free ballistic calculator, a rather sophisticated one from the Lapua site that works with these dragfunctions. You'll see then that BfX accurately reproduces its results.
The Lapua drag tables can be opened with a normal text editior. Then, bassically, cutting and pasting will put the table in Excel.
How does the custom dragtable work in BfX?
As said before, read the GettingStated workbook. Bassically however, you fill a range in Excel and supply it to BfX instead of the dragfunction string:
=bfx_vt(750;300;1;<range>). One has to use a ballistic coefficient of 1.
Expect in future other types of drag function. The next big project is the 6DOF extension.