Graybeard,
It kind of sounds like Remington didn't do enough testing before releasing the 5mm. With today's improvement's in powder and bullets design it could be an interesting cartridge again. Wouldn't it make an interesting comparison between the .17 HMR, 5mm RRM and the .22 WMR? Use the same make and model rifles to take out the rifle margin and just compare the cartridges. Lawdog