I fl sized Fed GM 308 to 7-08 and then turned off high side with OLD sinclair neck turner. The mandrel was very tight, and I used about 6 cases getting it where I wanted it. Used sizing lube. I could expand them with the Sinclair 7mm mandrel, but wondering if I could turn the 308 brass first. I have a separate 308 mandrel/screw in holder to expand before turning. Turn to neck/shoulder junction, then size to 7mm (FL RCBS die). Would this work? Any downside to doing this? Fired cases come out .317". The Fed cases are very close to .316" loaded, pre-turned. I got them to about .315 now. Factory specs are .316 to .317" taper. Thanks. Ron.