[Imp]

Guesses I have seen that seem more reasonable, DM53 as fired from L55 but if sources are to be believed there is very little in it between current latestGerman & US rounds. I have not seen any new guesses or Russian rounds for a while. These are I would say best case estimates when you eventually get verified data if ever tend to be about 10% over the top. Best to err on the safe side what people can field.
One thing that seems to have some basis in fact is US early guns cannot fire due to pressure problems. Also note Chineses m/s seems high
M829A1 : 1575 m/s , 700mm RHA @ 2000m
M829A2 : 1680 m/s , 780mm RHA @ 2000m
M829A3 : 1580 m/s , 880mm RHA @ 2000m
DM53 : 1670 m/s , 820mm RHA @ 2000m German
Charm 3 : 1534 m/s , 730mm RHA @ 2000m English
Du 3BM42M : 1600 m/s , 660mm RHA @ 2000m Russian
125-2 : 1720 m/s , 690mm RHA @ 2000m Chinese

To be honest as on my other computer cant say if takes into account diffrent way of measuring as in marks a steel plate at back or passes through etc.