Neck Reaming/Turning pilots

I am making some 6.5g from 7.62x39r.
This is my first go round with making different calibers....case forming.
I read quite a few articles that said you may need to neck turn some brass.
So far, I haven't found any that really need it.
But, being the compulsive spender that I am I got a neck turning attachment for my case trimmer.
And a pilot for 6.5mm. All that I've read says you ream/turn AFTER sizing.
That brings me to my question:
If you size the brass down to 2 or 3 thousands bullet pull, why would you want to ream with a bullet size reamer?
Wouldn't that eliminate some squeeze/grip from the brass on the boolit?
The pilot/reamer I got from RCBS was .264, same size as the boolit. not really boolits, I'm using the condom bullets for right now.
Seems the reamer ought to be .261 or .262.
Can you straighten me out?

The pilot looks bigger then the cutter. I would try 1 case. See now the bullet fits.

It really depends on how your setup is supposed to work. Some ream a fired case, some are for a sized case.

If cases are excessively thick, you have sized the brass several thousandths, then opened it back up with the expander, probably 0.261 or 0.262. If you ream with a 0.264 you are removing 0.002-0.003". You still have excess brass that you can again full length resize and then expand again to get proper neck tension.

So you probably wouldn't have neck tension on the case after it was reamed but after resizing you would.

Try one and see. If you don't have neck tension after resizing the case then the necks weren't too thick to begin with.

If you have fired cases, measure the outside diameter of a fired case compared to the outisde diameter of a loaded cartridge. The catridge should be at least 0.003-0.005" smaller for safety. Anything less thwn 0.003" difference, and you are getting into benchest/fitted neck territory.

Thanks for the info. I'll do some testing and see what happens.
It just seems to me that reaming with bullet size pilot kinda throws a wrench in the spokes, but...a lot smarter(and experienced) folks build this stuff they way they do for a reason.