I don't have the 6.5 M-D, but I do have the 30-06 JDJ in a rechambered barrel.
JD's velocity claims have been pretty close to what I've been able to achieve with the older T/C barrel I have which has the equal width lands and grooves. I think with the newer style rifling from T/C, it would do as good on the FPS with less pressure.
JD claims 165's @ 2700 fps with his barrels. I've gotten that from mine (2715 fps with 168's).
Regards,
Rog