BR,
Can you clarify which is the old and which is the new chamber. It looks like the top one is showing a recess for the rim. All the 1898s (total of 3) that I have seen are later than the 213000. They do not have the rim recess. Did early have the recess? If so the late bolts will not fit in the early receivers?

To add confusion the SAAMI drawings all show the recess. So you have to subtract the rim thickness to compare them. Not sure if you subtract the Maximum thickness or an average thickness. Neither seems to work out. If I am understanding your drawing the dimension changed by .030, which is huge.