SAC Modular Sizing Die - Bushing Size for 223 Rem

[fattybinz]

I'm loading 75gr Hornady Match BTHP bullets into starline brass for a plinking bolt-action rifle. I'm ordering a SAC modular sizing die but I've never had a bushing die before so I'm not sure which size to go with. SAC has two calculators to help with the size: One goes off of the loaded neck diameter, and the other uses one-sided brass thickness. Both methods give me two different bushing recommendations that are .002" different. Wondering which is a more reliable method. Below are my inputs and what is recommended by the SAC calculator. Last questions: I thought the standard way to calculate bushing size was to take the loaded neck diameter and subtract .002". Should I just go with that instead of the below two suggestions from SAC? Also, 001" neck tension is okay for a non-hunting rifle if I do not plan to load longer than touching the lands, right?

Loaded Neck Diameter Method:

My inputs:
Neck Tension Desired: .001"
Loaded Neck Diameter: .248"
Calculator:
Bushing size recommended: .0243"
Mandrel Needed: .2235"

One-Sided Brass Thickness Method:

My inputs:
Neck Tension Desired: .001"
One-Sided Brass Thickness: .0125" to .0135", average is .0130
Calculator:
Bushing size recommended: .0245"
Mandrel Needed: .2235"

 

[chromatica]

I like to go with .002 neck tension plus .001 springback, so I subtract .003 from the neck diameter of a loaded round. BTW, use a dial caliper for this measurement; digital calipers don't have the accuracy and repeatability you need.

 

[Sandstorm]

Also get yourself a couple mandrels to finish the job to your liking.
I like my SAC die, works real well with the custom bushings.

 

[memilanuk]

: I thought the standard way to calculate bushing size was to take the loaded neck diameter and subtract .002". Should I just go with that instead of the below two suggestions from SAC?

I think their calculations are probably taking into account some spring back, both after sizing the neck down, and then mandreling it back up. Some people have found that moving the neck a tiny amount to be less consistent than somewhat larger movements. Of course, as with all things, there's a limit on that as well.

Also, 001" neck tension is okay for a non-hunting rifle if I do not plan to load longer than touching the lands, right?

Or feed it roughly from a magazine, or keep it in your pocket, or... you get the idea