Dimpled brass

Okdeerman

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Joined
Mar 9, 2021
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24
Location
Oklahoma
Anyone have an idea why this is happening. It shows no sign of excess pressure. I chrony every shot and this one was about 30 fps slower. This is a 6.5-06. The brass was made by sizing 270 brass down and trimming excess length.
 

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I am using 53.5 grains of iMR 4350. My velocity does not vary much. Running usually +or- 10 to 15 fps at 3210. The accuracy is real good. I might try 1/2 to 1 g higher. The higher the velocity the flatter the trajectory. 😀
 
Hey Wambo, the bullet is a 123g Hornady SST. The barrel is a 26in McGowen Precision, 1in 8 twist. Recoil is easily manageable, I love it. This is my 3rd McGowen barrel and they have all been more than acceptable in accuracy.
 
I also had this happen fireforming 25-06 AI brass trying to seat the bullet into the lands. The bullet left the neck early in the pressure curve. Are you by chance seating your bullets long with minimal bearing surface in the neck?
 
I would seat deeper. You may not have much more room pressure-wise to add powder and would probably still have the same issue.

As long as you are not trying to fireform an ackley shoulder and are pushing the 270 shoulder back to the correct headspace dimension with the sizing die, I would seat the bullet into the neck so that the bearing surface of the bullet is just forward of the neck-shoulder junction(option 1).

At a minimum, I would seat the bullet with bearing surface halfway into the neck. (option 2)

It really depends on how the rifle shoots with the bullet seated deeper.

I prefer option 1, and usually have the freebore set for my bullet 0.020" off lands at this seating depth, if possible.
 

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