As diving instructor, with a long experience in charge diving air cylinders, I always see a problem when the air blown in the barrel solution is suggested: the humidity condensation generated by the compression and expansion of the air.

I prefer the opposite solution to suck up the air thru the barrel from the muzzle. No concentrated humidity air sent in the barrel.
It is better IMVHO.

That walmart air blower that I suggested will also work as a vacuum if you attach the hose to the other end of it. Just FYI.

I do most of my load development in the fall, winter, and spring. I mostly shoot for fun in the summer - revolvers and shotguns mostly. The way I see it, the majority of my hunting (so far) has been in fall or winter-like conditions, so I prefer to develop loads in a comparable climate. It is amazing how much faster a rifle barrel will cool in a brisk fall day compared to a hot summer day. In winter I take a thermos of hot chocolate, a few disposable hand warmers, and some warm clothes (no PAST pad needed), and it is all good. To keep warm, I walk to the target very often as I am usually the ONLY one at the range - quite pleasant actually.

Furor,
thank you, I don't know walmart air blower and my suggestion was based on my experience. During an air cilinder recharge if air is humid it can be clean a table spoon of water from the filters of the air compressor. Ad at the end of the diving summer season a cylinder can contain a glass of water even if the filters have been carely cleaned during the cylinders charging.

A lot of good ideas with a shared problem here.

I like the idea of moving ambiant (sp?) air through the bore, but I'm not coming up with any practical solution. Actually caught myself looking at a Black & Decker 12V leaf blower. Then I pictured myself at the public range that I use, giving a blowjob to my rifle with a leaf blower, and decided that was a bit over the top.

So until somebody comes up with something more reasonable, I'll have to try some of these other ideas involving cooled liquids.

Liquid nitrogen's cheap at welding supply stores.