You will definately have less chance of them fragmenting at a lower speed/powder charge. You might try the 270 grain platinum powerbeltsat 80-100 grains of powder. In Nimrodder's case, he was using about 115 grains equivalent to srwshooter's 100 gr load since he was using loose powder vs. pellets. Loose powder is supposed to be 15% stronger than pellets.

Don't buy into the hype that you have to use magnum charges of powder. Remember the revered 45-70 caliber that killed millions of buffalo? It is 45 caliber and used 70 grains of black powder.