As I understand it, the .262 neck came about from the combination of the thickness that Sako .220 Russian cases had to be turned to to clean up, and the desired clearance between chambers and loaded rounds. Later, when Lapua cases became available, the .262 neck has continued because reamers and bushings would have had to be replaced for a different size, and the existing size seemed to be working pretty well, which minimized the incentive to make a change.
A few years back, some bright fellow, who was an experimenter by nature and well enough funded to disregard the cost of a reamer and a couple of bushings looked at the situation and decided to try a larger neck diameter, given that the Lapua brass would clean up at a greater thickness. The .269 neck chamber was the result, and by all accounts that I have read, it has shot as well as .262, with the added advantages of being a little easier to turn for, and greater resistance to being dented when used in conjunction with an ejector. I have also read of .261, .263, and 265 chambers, but these seem to have gotten less attention. To my knowledge, none have offered any particular accuracy or case life advantage (or disadvantage).
At the present time, if I were ordering a new reamer, there are a couple of factors that might cause me to change from the .262 neck that my current one has.
One is the previously mentioned ejector. A thicker neck would undoubtedly be more dent resistant in that application.
The other reason would be to be able to go back to the neck thickness that I had before switching to a larger neck to chamber clearance. The clearance that I used to use was around .0015 +-and the current clearance that I use is closer to .003. It has seemed to me that 133 likes about as much neck tension as can be managed with necks turned for more traditional clearances for a .262 neck, and that thinner necks seem to require slightly less force to seat bullets. Adjusting for this difference would only require increasing my chamber neck diameter to .2635 or .264.
On the other hand, we are blessed with a couple of new powders that seem to be producing very good results with slightly less neck tension than 133 likes, so I have taken a wait and see attitude.
As far as the longevity of cases is concerned, I have not had much of an issue that way, I don't remember ever having a neck come off a case, but of course mere case survival is not the only, or most important issue.
One thing that I have been careful about, that may have contributed to my case necks staying attached, is the radius where cutters' leading angles meet that part of the edge that is near to parallel with the turning mandrel. I have seen cutters that were a little too sharp for my taste at the apex of this angle, and have remedied this by a small amount of stoning. Also, a friend has a turner, that does not seem to have any significant leading angle, which causes the leading corner to dig into the shoulder. I would not have this configuration for my use, but he is only taking a light cleanup cut for a close neck chambered BR, so it has not been a big deal.
For competition, it is obvious that if one can shoot smaller aggs with fresh brass, then worrying about getting the last gasp out of cases would seem to be false economy, given all the other costs of shooting matches.....but I think that this is a matter that should require some testing to determine. One issue in this would seem to be how a particular shooter tunes. Not all good shooters take the same approach to bullet seating depth, choose to be at the same node, use the same powder, or have chamber bullet combinations that have the same length of bullet shank in their cases necks. There factors may combine in different ways which result in differences in how important having fresh brass is.....I think.
Of course you can always pick some winning shooter and simply copy what he does, which, after all, may be the simplest approach, particularly if your primary goal is to develop an effective procedure with the least delay.
