Question about measuring for bushing size and neck tension

[Jpw2]

Here is my confusion... I have a box of factory Nosler 190g Accubond 300 Win Mag. I grabbed a round from the box and the external dimension of the neck reads .3345. I also have two brand new boxes of Nosler prepped and ready to load 300 Win Mag brass and that same measurement is .3325.

My question is this... if I am using a brand of brass, i.e. Nosler, and I buy a box of factory loads, will measuring the factory loads with the bullet still seated give me the measurement to subtract the .001 or .002 from to know what bushing to buy? Or do I need fire off the factory loads, reload the round without setting any neck tension and use that measurement to establish the bushing I need?

Please help me understand what I am supposed to take my measurement from so I order the correct bushing(s)... thank you.

 

[NiteQwill]

You cannot have two different brands of brass and expect to get the same measurement. This is due to the differences in the thickness of brass across the spectrum of manufacturers.

This is a big reason many people have many bushings around the same ballpark. For example, for 6.5 Creedmoor, I have bushings from 287 to 292 - because I may use Hornady, Lapua, or Peterson brass, for example - which all have DIFFERENT thickness.

The difference in bullet within the case will also vary on the neck thickness (and with annealing and with other factors).

My suggestion if you want consistent reloads or "one bushing:" stick to one brand of brass.

 

[Supersubes]

Bullets are very consistent in diameter which makes them a great “anvil” to measure off of. So measuring a loaded round is the way to go. Measure the factory rounds and subtract .002-.003.