Load development with new brass?

zr600

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ok if I did load development with my 6.5 creedmoor and Nosler brass that was brand new never shot and found a great load how would you think that same load would be with the fire formed brass after being sized? Or am I over thinking it?
 

gte901m

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Should be within a few thenths of grain with fire formed brass. Shoot a follow up test. If time was limited, I’d reshoot the previous optimal, +.1, and +.2.

In reality, if minor brass dimensions and/or a .1 grain shift causes groups to scadder, then it wasn’t a optimal charge weight to begin with.
 
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gte901m

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Additional thoughts:

Next time you get new brass, seat a fired primer in it backwards and measure the water capacity. Repeat for fired brass, and that will give you an idea how much case volume changes from new to fired. The change in water capacity is not a 1:1 with powder, but it will let you know if volume is changing by .2 or 1.2 grains of water. If it changes by a small amount, powder should change by a small amount.

Neck tension on new brass is normally a thousand or so tighter than resized brass. Changes in neck tension can have an impact. I eliminate this by running an expander through the neck on new brass.
 

Lonewolf74

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As has been stated you should be close but most likely would need to back off a couple tenths or so on powder.

This is where a chrono can be handy. If you where in a good node with the virgin brass you should be able to just change powder charge a few tenths or so to match the velocity you had in the virgin brass.

Typically virgin brass acts as a buffer or absorbs more pressure while forming to your chamber to give you a little less velocity per charge weight. For example a load i have is 40.4 gr of powder giving me 2950 fps in fired brass. In the virgin brass I have (all the same lot) my load is 40.8 gr to match that velocity.
 

RegionRat

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Bottom line is you know you will have to test.

If a minute difference in case volume gives a significant difference in performance, and you are sure it isn’t due to something for example neck tension, then you were not on a stable node to begin with....
 

J E Custom

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One reason I like to fully prep new brass is to eliminate as many changes to the brass that I can. Size, trim, turn, de-burr and weight sort, so the only difference will be the slight change in volume.

Sizing, trimming and turning will keep the bullet grip consistent and also help to form the case concentric with the bore and chamber.

I have also found that first firings can be very accurate if all brass prep is done in the beginning, even on wildcats that undergo major dimensional changes.

J E CUSTOM
 
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