Re: redding s type bushing resizer
^ this, (.002 is accepted by most as minimal amount of sizing for minimal neck tension) You can always go more, .003, and .004 is acceptable. If you are not crimping hunting loads, greater than .002 might be wise.
another method is to take caliber, example, .308, add at least .015 (broadly accepted min value of neck thickness for factory chambers) x 2 (there are two sides of the case) .308 + .030 = .338
this is best for general estimate, If you turn your necks, and or other rifle and brass variables can change this.
If you feel .338 is too loose (not enough neck tension on bullet) you can always go down .001 or .002 to a .337, or .336
I use a .338 on my 300 Rum, it works great
again there are more precise ways of getting it just right, measuring case neck thickness, measuring neck diameter of fired round and plug those numbers into an equation. {(thickness of brass of case neck x 2) + bullet diameter} = x then Diameter of your fired case from your rifle - x = y, diameter of fired case - (y + your desired neck tension) = bushing
example
thickness of brass at neck measured .016 x 2 = .032
.032 + bullet diameter .308 = .340
diameter of neck of fired case = .343 - .340 = .003
diameter of neck of fired case .343 - [(.003 + desired neck tension .002 in this instance so (.003 + .002 = .005)] then .343 - .005 = .338 that would be my bushing size
hmmm does that make sense??? i always hated math, sure there was a better way to do that...... oh well hopefully i helped and did not hurt