Shoulder bump

[Garbageman]

Trying to refine my loads for my RPR in 6.5C. Was using hornady brass/bullets, now I'm experimenting w/ alpha brass and berger 140's. I'm using a redding FL 9X die

The hornady brass after firing measures 1.5295 to the shoulder using a whidden shoulder bump gauge. The alpha brass measures 1.5268. I measured five cases and averaged.

Both have been fired twice. Why is the hornady longer? Brand new alpha brass measures 1.5250.

So, do I set my die to push the shoulder back to 1.5248 (1.5268-.002) on the alpha brass?

 

[Carlos Danger]

Fired brass should measure longer than virgin brass as its expanded (fire formed) to your chamber.

Bump your shoulder back .0015-.002 thousandths based off the fired brass.

 

[Garbageman]

I understand that fired brass will be longer than new brass but I'm curious as to why the fired hornady brass is longer than the fired alpha brass, referring to the measurement from the base to the shoulder. Both were fired from the same rifle.

 

[Carlos Danger]

I didn't read the both fired twice part.

 

[Baron23]

Eh, thicker or diff brass alloy, perhaps,

 

[John Glidewell]

Different wall thickness and spring back. I set shoulder bump by fit in chamber. I run Big Horns and remove the firing pin bayonet so there is no tension on the bolt when it closes. size brass until I can just barely feel it touch on close then go .001 more on bump. You can watch the sizing video on this site below.

Videos | wheeleraccuracy

www.wheeleraccuracy.com

 

[straightshooter1]

Trying to refine my loads for my RPR in 6.5C. Was using hornady brass/bullets, now I'm experimenting w/ alpha brass and berger 140's. I'm using a redding FL 9X die

The hornady brass after firing measures 1.5295 to the shoulder using a whidden shoulder bump gauge. The alpha brass measures 1.5268. I measured five cases and averaged.

Both have been fired twice. Why is the hornady longer? Brand new alpha brass measures 1.5250.

So, do I set my die to push the shoulder back to 1.5248 (1.5268-.002) on the alpha brass?

Because different brass can have different thicknesses AND different a difference in hardness, there's going to be a difference in spring back. If you anneal the cases after every firing, you should have much less difference in spring back than .003.

If you're going to use the same die to size both cases and not anneal, yes . . . you'll have to make a die adjustments to get the same bump measurement for the two brands of brass.

 

[Yondering]

Trying to refine my loads for my RPR in 6.5C. Was using hornady brass/bullets, now I'm experimenting w/ alpha brass and berger 140's. I'm using a redding FL 9X die

The hornady brass after firing measures 1.5295 to the shoulder using a whidden shoulder bump gauge. The alpha brass measures 1.5268. I measured five cases and averaged.

Both have been fired twice. Why is the hornady longer? Brand new alpha brass measures 1.5250.

So, do I set my die to push the shoulder back to 1.5248 (1.5268-.002) on the alpha brass?

As said above, it's because the alpha brass needs to be annealed. Maybe they both do, but spring back due to brass hardness is the cause of what you're seeing.

Also, just FYI - shoulder bump is not so precise as to need measurement down to 4 decimal places. You'll see a lot more variation than that between individual pieces of brass in the same lot. Just round to the nearest thousandths and you're fine.