Reloading .303 British : Inside neck reaming...

I did not detect the donut on the fired .308 cases using pin gages. I’ve probably reloaded these cases 8 to 10 times.  I neck sized these cases in the Lee Collet die, so unlikely to form the donut during sizing. 

I seat the 168 TMKs to 2.950 OAL to get within 0.025 inches from touching the lands. This also increases case capacity and lowers pressure. The bullet bearing surface is forward of the neck/shoulder junction, so very low risk of a donut causing any pressure issues. 

So, this seems to be a condition only associated with my .223 loads with 80 grain SMK.