I think one reason that .262/.263 necks remain so common is that people are hesitant to change something that works for them. Nothing wrong with that, but a lot of people continuing to use a .262 neck doesn’t necessarily prove anything about whether a .269 neck can compete.
Also, for people with a lot of barrels, it becomes a bit of a pain to go through the transition of making cases for both. If you only run one or two barrels, this is not so big of a deal. In my case, I have 3 PPC bag guns and a rail, so once I committed to the change, I either had to dice the barrel, or rechamber with the bigger neck to keep everything in my gear consistent.
I always used to turn .263 cases with 2 passes. I never liked turning brass, so the option to cut my workload by 50% had some appeal. If there is any cost saving in running bigger necks, it is the fact that I only needed to dedicate one turning tool with carbide mandrel, whereas the tighter necks I was using required me to dedicate 2 neck turners preset to the two different cut I needed to make.
After seeing results from some early experimenters that seemed to be getting aggs consistent with thinner necks, I made the decision to order a .270 neck reamer. As noted, a .272 neck is basically “no turn” with Lapua brass. I believe my actual reamer dimensions give a neck cut closer to .269 than the .270 I specified, but I’d rather that that be out the other way. I run several thou clearance in my loaded rounds, so I still take off plenty of material from the case neck. There is no way I am only making partial contact over the full neck length.
In terms of effectiveness, I am convinced the .269/.270 neck gives-up nothing to thinner necks. For example in South Africa for the WBC in 2009, many will know that Australian teams placed 1st and 4th. What may not be so well known is that I believe 10 out of the 12 Australian competitors were using .269/.270 necks. Just highlighting this as I don’t think the case neck thickness was any kind of a handicap. I went to a .270 nominal neck in 2007, and have personally shot my best aggs in that time.
Another benefit of thick necks that I never anticipated is that necks seem to grow at about half the pace of thinner necks. One other consideration – if you are planning to use Norma 6PPC brass, you may want to stick with a .262/.263 neck, as a .269 will pretty much be a no turn neck.