That being said if handed a pristine rifle and if it was properly maintained after 10M-20M rounds (I would think) would be a call for a new barrel.
Shouldn't that be 10K to 20K rounds?
In one sense it does.
In common references to currency, M or m denotes million or millions, such as $25M (twenty-five million dollars).
However my meaning was thus:
In Roman numerals, M denotes one thousand. While the symbol had originally a different shape, it took on the shape of an M based on the association with Latin Mille ("one thousand").
It is what we use all the time at the shop for a quantity run.
5M low head 1/4-28 socket caps = 5000 units.
So in this case I posted number of rounds fired as units and referred to the M as being 1000.
Sorry for the confusion.