I have a plastic ammo box that I have marked "range use" and when I need to de-chamber a round, I put it in this box. Once I have chambered a round from the magazine, I don't re-chamber it until I am at the range.

Now, I've read conflicting reports about loading a round directly into the chamber, versus loading it from the magazine. Some say it harms the extractor, while others say it is isn't an issue with external extractors like it is with internal extractors. (I don't know for sure, but I don't do it.) I saw my local gun smith do it, after he handed me his personal SIG P239 to handle; he dropped the round he had removed from the chamber before letting me look at the gun, right back into the chamber. His opinion was that it didn't hurt external extractors, and that it prevented the bullet setback issue from repeatedly re-chambering the same round from the magazine. He said he wouldn't do in on a 1911 (or any other gun) with an internal extractor.