Been doing this a long time.
Measure the neck of a loaded round, 5 is even better. Get an average of what the thickness is.
Now, order bushings -.002 & -.003 smaller. You will see a difference in how a gun groups with the different size of bushings. I have one rifle that shoots slow powder that uses a -.004 bushing.
I always start off with the -.002 and go down from there.
You won't know....till you know.
Measure the neck of a loaded round, 5 is even better. Get an average of what the thickness is.
Now, order bushings -.002 & -.003 smaller. You will see a difference in how a gun groups with the different size of bushings. I have one rifle that shoots slow powder that uses a -.004 bushing.
I always start off with the -.002 and go down from there.
You won't know....till you know.