I am having a chnge of religion from 6.5x55 to .260 Rem. I have necked up some Lapua .243 cases using a Sinclair expnder mandrel, first to .25cal then to .26cal. Then I put the cases through a Redding body die to set the headspace and lastly I passed them over the .26 cal mandrel again. This left a nice fat donut on the outside, not a problem to turn it off as I must neck turn for the .290 neck anyway. However when I put the case on the neck turning mandrel (Sinclair) I can feel some (not much) more resistance at the base of the neck. Is this going to be a problem? or will outside neck turning the donut away solve the problem if it is just neck tension that will go after the first firing or should I inside neck turn? What I don`t like about the idea is firstly can I do more harm than good if the inside neck turner is not a perfect match with the inside of the case neck,not sure if my RCBS case trimmer is up to the job. Also when should I do the inside neck turning, Forster say for most cases after first firing unless you have a special reamer made up. Also if I do it what is the best reamer to fit my RCBS case trimmer? or should I just use the RCBS inside neck turning pilot to do the job. Thanks in advance, David.