I've shot the 6mm in both long and short actions. The Remington short action is about the minimum it will work with when using some of the longer bullets, unless you seat the bullet deeper than the norm. No big deal, but still there. When using bullets like 105grain AMAX, and wanting to be close to the lands and grooves the long action is a little better, unless your using a longer short action. The Savage is roughly .18" longer and the Winchester is roughly .15" longer, and this certainly helps in these matters. I think in the Remington, the 6mmx55 improved would be ideal. Plus the velocity loss would be very minimal at the worst. To add to this issue, one needs to also take notice of the internal magazine length (not sure, myself as my one short action has the magazine filled and converted to a single shot). Of course if your just shooting 85 grain bullets this is not an issue to worry about. Plus the lighter bullets become another issue in the longer actions when trying to eliminate bullet jump.
gary