I would think if this were to cause a problem, it would be hard chambering rather than hard extraction since normally they head space on the rim and the cases free float in the chamber.
If the 47 cartridges chamber ok, they will fire-form to the chamber pretty much to the same dimensions that the 70's will. So I think your extraction problem is caused by something else.
BTW my 65 Czech silvertip is a pretty close dimension match to the 47 Russian factory 188 that I recently got:








