150 grainers CAN work fine in a 1 in 9.45" (standard Mauser rifling rate) barrel. Those who haven't gotten them to work just haven't found the right load combination. I've shot tons of them, with very good accuracy.
As for heavy bullets, you can go as heavy as you wish - with one proviso. Be aware that, the heavier a bullet for a given diameter, the LONGER it is. At some point, you will run out of room, so to speak. That is, beyond a certain weight, you won't be able to chamber loaded rounds, unless the bullets are seated so deeply in the cases that gas blow-by and bullet base deformation becomes a problem. (And jambing the bullets into the rifling upon chambering, with anything but LIGHT loads and CAST bullets, is very dangerous.) The longest/ heaviest I've ever gotten to work in my Mausers has been approx. 215 grains. I know that you can go beyond this - somewhat. But, 235 grainers are too long for most Mausers (they certainly are for mine). So, the "limit" is somewhere between 215 and 235 grains, for most Mausers (if not all).
Really, you'd be better off with a bullet in the 175 to 200 grain range. You'll find the least difficulty in achieving a good load, if you stay within that range.