I took advantage of the first cold snap this morning, to see if the cold affected my TX 200 tune , Luckily I had one action in the garage : cold +1 degree, and another in the house warm +20 degree, both guns have aluminium pistons and aluminium ( hard anodised) comp tubes with x ring seals lubed with krytox, one has a slightly longer stroke than the other . I chronoed both guns and running at 800 fps with a 3-5 fps spread with aa express, as I had set them up previously. Swapped them over and let the cold one warm up and the warm one cool down . The warm one cooled down over the course of the day to +3 degrees and chronoed at 802 with the same spread . The cold one warmed up to +18 degrees and made 800 fps with the same spread as before . Not very scientific, but looks like they aren't altering power with temp change unless something drastic happens as the temp drops further , fingers crossed .