I doubt seriously that you will ever be able to tell any diff in performance when you keep shells in that temp range. excessive heat or extreme cold might possibly have some effect but new shells should not show anything. some primers used in reloads with certain powder configurations have been known to have problems with extreme cold, but have never heard of new shells having such problems
still shooting a few AA's from the 70's and some RXP's, that were stored in a barn since they were bought, and no electricity in it, so you can imagine the temp. variance there. No problem.......shot a couple of boxes of bob whites over thanksgiving, stored in same place and no problems there either, and they are a paper shell.
What about humidity and it's effect on performance? I live near the coast, lots of rain and fog. I keep my reloads up high and dry, but no dehumidifier in use or heat. It gets down to about 40 degrees in winter. Thanks
Had some reloads with WW473AA and some with Red Dot stored in unheated garage for 19 years when our local trap range closed and I didn't shoot trap and all fired right, had to scrape some corrosion from the brass with fingernail on most of them. Ed