Bill Davis did a test for
American Rifleman in March 1991 with the .244 H&H Magnum. This was a full-length H&H case firing a 100 grain bullet at an advertised 3500 fps. After 300 rounds fired, the throat had extended 0.150" and chamber pressures increased with the same loads. It required charge reductions of 10% or more to keep the pressures at acceptable levels, and velocities were reduced by 150-200 fps. The throat was so rough that it was damaging the bullets enough that occasionally they would break up in flight. This experiment was performed with two different barrels, with identical results.
Since the RUM case holds considerably more powder than the H&H case does, I'd assume the issues would be even more extreme.
Run away as fast as you can.... 