25 creed neck tension help

[.7mm.]

Trying to determine which sizing die or neck bushing size to buy for my 25 cm.
Using alpha brass and a 21st century. 255 expander mandrel (actually its the black nitride turning arbor which is 2 thou under bullet diameter)
Right now with the Virgin alpha brass the mandrel just plops right into the case, while the .256 expander i also have will actually expand the neck but im not sure if I want to run 0.001 (or 0.0015 with spring back) yet. Maybe I will later once the rifle tells me what it likes.

But right now should I just go with the Virgin alpha brass neck tension the way it is? Seems like they are all pretty uniform but I don't have pin gauges and can't really trust my mitotoyo to that degree.

Also looking at the f class products 25 creedmoor sizing die in the 282 neck od for my sizer...is that going to be sufficient in giving me enough initial neck tension so I can then expand using the 2 thou mandrel? Or do I need to look at the SAC bushing die

 

[Phil Rizzo]

Make a dummy round and measure neck OD. I'm sure AM brass is very consistent. I'd mic the bullets you intend to use, also for reference.
At least you will have starting points to begin with, no matter where you end up.
I'm in the habit of using bushing die and mandrel on virgin brass.

 

[Justice1327]

I chamfer and load new brass. This helps with fireforming the brass to your chamber better. after your brass is fire formed to your chamber then you can look at serious load development. Once you find your powder and seating depth then you can play with neck interference. I was using 1 1/2 to 2 1/2 Thou but have now started using 4th. So far so good.