Crusin, i'm here. sorry it took a while. what you need is a device that has interchangeable expander mandrels.i'm pretty sure Sinclair makes one but i don't know what it's called. mine is not a Sinclair but works the same. the outside is a 7/8 thread that screws into the press and the center is threaded to hold whatever size mandrel you need on the bottom.the mandrels have a tapered beginning,maybe a 3-5 degree slope that ends up at slightly under bullet diameter. hopefully about the same diameter as your mandrel for turning the necks. this operation is performed on your reloading press with the appropriate shell holder.just push the shell up over the mandrel and pull it back off.i use a generous amount of resizing lube.once the necks are pushed out,i run them through the FL sizer to straighten them out, as some are noticeably crooked.
i was told by 2 people that had this round that loaded ammo was 365 in the neck so i ordered a 368 neck on my reamer and 362 in the FL die i got from Forster.when i finally got some loaded they were 368 in the neck so i have to turn mine. wasn't what i wanted but that's what i got. i've only used Rem brass so far.i'll see if i can find what Sinclair calls their product. it's great for any new brass, as you know most of it is rather lumpy in the neck,and this tool will make it perfectly round. hope this helps.
the tool is called a Sinclair Expander Body. #NT-EXP. you'll find it in the reloading equipement,under neck turning tools.just buy whatever neck turning mandrels you'll need for every caliber you own, or think you'll ever need.