NOE .312 expander plug problem? loaded rounds wont case guage when finished?

You cannot expect a manufacturer to predict the expanded ID of the case mouths for your cases. Brand, thickness, number of firings and work hardening of the brass all contribute to sized ID of the cases. You need to figure out what a .310 or 0.311 diameter expander expands your cases to.

For a 0.311 diameter bullet I would use a 0.311 expander for target ammo. The brass should spring back 0.0005-0.001" from the sizer diameter. Again, depends on your brass. For hunting loads and/or tube magazines I'd use a 0.310" expander for 0.311 bullets

Again YOU need to find out what works for your brass.

A 0.308" expander may work for some people with hard boolits, but I shoot soft alloy and like my neck expander to be boolit diameter of slightly smaller.

IMO, manufacturer doesn't need to predict expanded ID of the case, exactly, to know that expander plug 2 mils smaller than a jacketed bullet is all but useless. The case will contract. If it does not contract more than 1 mil, the case will not get good neck tension, and it doesn't matter how large or small you expand it before seating. Once the bullet is in, there will not be much elasticity holding it there. This case is garbage.

There is no way an expander same size as the bullet is going to ruin neck tension. If you gots no neck tension your brass is bad or your sizing die is too big and/or case necks too thin, or all 3. The main danger, I suppose, is if you change to a smaller bullet and forget to change your expander plug.

Going with expander larger than the bullet by up to a mil, yeah, you would have to pay a little more attention to make sure everything is good to go, but same idea. If you're not getting tension, the problem is not the expander. IMO

Quote:

[I] like my neck expander to be boolit diameter or slightly smaller.

I like my expander to be boolit diameter. Maybe even a hair bigger at the case mouth, say half a mil, and an ever so slight taper down to bullet size at the end is maybe even better. But now I'm just theorizing. I haven't made any that exacting. :) Actually, in rifle, it doesn't matter (to me) so much, cuz I find commercial gas checks are quite hard.

If I were making expanders for a living, I don't see any point in offering one smaller than the diameter of a jacketed bullet, whatsoever. Other than (misguided) market demand, of course. I see CYA at work. End user has to determine how deep to expand pistol case for the bullet, and has to have a functional brain to know when to use roll crimp on rifle rounds where necessary. If you only recommend people use uselessly tiny expanders, they can't blame you for setback.

The only place I can put a real benefit on "industry standard" expander is for jacketed rifle round where in some very specific scenario, it might allow you to avoid roll crimp. Also, trying to use a standard pull thru rifle expander in a "proper" size may actually destroy the brass in the process. If it's more than a couple mils of expanding, you need to do it push thru.

Why don't you email Al Nelson at NOE to get his take on your issue?