13 April 2018
I do not know at what velocity the calculations are for but, I work in the lower supersonic range (~1470) and have tested several of bullets that I have and have witnessed several others as well as, gotten the results of two other bullets that were tested on Barry Darr's M43 ballistic lab. In those tests, most bullets had BC's very close to the calculated BC's on the TMT program. Two bullets had higher BC's than calculated.
All of the bullets that I have info on were of a spitzer design, with meplats of .080 or smaller. The one exception, to those tests is a 33 cal bullet that I designed and had Steve Brooks make. It had a .080 meplat but, was a little to long for the twist. It's designed BC was .491 and the actual was .375. I assumed the reduction was because of the nose wobbling in flight.
BUT, you may have a point that the MX 30-ARD doesn't actually have the designed BC. That because of the large meplat of .130. But, I would be very, very supprized if the BC was less than .38. Much of the calculation is based on the ogive radius but, the flat of the meplat will effect it, if it to large.
Even though a meplat is small, a short nose still acts much like large meplat, in that the air will have a lot of trouble following it's contour, especially in supersonic flight.
How was your BC measured?