Hi, guys,
After I posted that it is perfectly possible to close the bolt on a chambered round in the Mauser, some folks replied that it is true of "late" Mausers, but not "early" ones.
So I just tried it in an 1891 Argentine, 1893 Spanish, an 1894 Swedish carbine, and an 1896 Swedish rifle. No problem at all. The extractor will not easily snap over the case rim when pushing forward on the bolt, but in all Mausers, the closing cam range is within the dimensions necessary to engage the extractor on the case, so moving the bolt handle down to the locked position will (and does) result in the extractor gripping the case.
I can't say that there are not some Mausers in which this will not work, but they would appear to be out of spec in some way. I believe there is ample evidence that the rifle was designed to allow (if not encourage) single loading.
Jim