I use "CHamber Chillers" on most of my long-range rifles. I invested in a couple of USB power units and have one in each of the cases. Since I only am interested in "first shot" for varmint hunting, I check all of my groupings on cool barrels. I typically will "burn through" a hundred or so rounds each session. My retched back and neck rebell after a couple of 10 round strings, so I use that time to relax behind the line and let the barrel cool. The chamber chillers also act as an "empty chamber" flag for the rso's. Most of my rifles cool down sufficiently for the next round except the 338 LM, that barrel really gets warm. Takes about 15 minutes before I put it in it's case, don't want the padding material to "melt" Ha HA.