Originally Posted by
bogie
Are you using a factory crimp? If not this will reduce velocity spread and give you the tension you need.
I like your sorting process. I'm assuming manufacturers are consistent in producing cases with uniform thickness. That seems reasonable if the cases are similar vintage. One thing to consider...If you are cold working the brass a lot during reforming to 260, you could be getting some residual stresses in the case that will result in non uniform neck tension. Have you tried annealing?
Anywho, new brass seems the best way to go for your match.
Looking forward to the camera footage if you decide to post it.