I've loaded and shot all the Berry 124gr bullets. All Berry's FP bullets end up seating deeper because that nose style bullet brings the .355 diameter out much further than say their 124gr RN. So you do end up with a shorter OAL than any weight Berry RN.
I found that the HB void is not large enough to allow the bullet to expand to fit the bore, it's seems there merely to lengthen the bearing surface. Another nice thing was that it seems to hold about 0.2gr of powder, so if the short OAL is getting you near compressed load territory, then using these will add some insurance.
My testing showed they also shot better than the 124gr Berry HP, too.
No need to significantly adjust the powder for any Berry 124gr if you're doing target loads. I generally use 4.3gr of Win231.