Dug out my copy of "Bolt Action Rifles, Revised Edition", by Frank de Haas; his comments on the Model 23 headspace were as follows: "The Model 23 was also prone to develop excessive headspace, and I believe this was due largely to the fact that neither the receiver nor the bolt sleeve were hard enough to resist wear. However, I discovered that this problem, when it develops, is quite easily taken care of by making and placing a washer of the correct thickness between the bolt sleeve and the bolt body". I've got a 23D from the mid-thirties which has no problems yet. I'm the 3rd owner; my buddy got it from the original owner in 1966 and I've had it since about 1997. I load for it but it doesn't get hot rodded or "K'd" because I've heard of those headspace issues. Mr. de Haas also mentions that the 23-D can be rechambered to the K-Hornet but that it is not much of a choice. Sounds like he wasn't very fond of it in a 23 series.
