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Old April 10, 2013, 07:24 PM   #1
Freebird
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Pushed Primers

Hi All, had a question for the resident experts. I have a new 6.5 Creedmoor factory rifle. Anyway, I shot 120 rounds of factory Ammo (140 GN) and upon measuring the fired brass I noticed every primer was pushed out a very very small amount. (.001-.002 tho) I then reloaded a batch and fired them with the same results. The loads were well under book Max but high enough that I don't think it is a Underpressure situation and positive it is not an overpressure situation. I noticed when I loaded the brass the primers all sat with very little resistance compared to my rem .308 brass. Some felt like they had no resistance at all. (Brass only fired once from factory) Anyway, I have a headspace no-go guage on order to check headspace but I did try and close the bolt with a piece of .004 masking tape on a primed unfired piece of Brass (bullet and powder pulled) and the bolt would not close. I am confused....Maybe soft Brass? Maybe .002 headspoce? any thoughts?



Thanks in Advance

Chris
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Old April 10, 2013, 07:54 PM   #2
mehavey
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The protruding primer make me think headspace and low pressure, but If it won't close w/ a 0.004" shim,
it doesn't sound like headspace. At the same time the loose primer pocket sounds like high pressure.

`Tis a puzzlement.....

Can you tell us the dimension of the brass with protruding primer, and then extend the decapping spindle
max to punch the primer (but not size) and measure again?

Also, who manufactured the brass?

Last edited by mehavey; April 10, 2013 at 08:02 PM.
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Old April 11, 2013, 06:03 AM   #3
Freebird
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Thanks for the reply. The brass is all Hornady.


As far as potential sizing goes I ran 1/2 the brass through a neck die and the other 1/2 through a de-cap only die so I am 100% sure it is the primers and I am not bumping the shoulder. At first I though my neck die was messed up and it was bumping the shoulder so I tried another die with the same results. I even smoked a few cases to verify there was no contact.

I can get exact measurements when I get home but they are all .001-.002 shorter after I remove the primers.

Thanks again.

Chris
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Old April 11, 2013, 06:13 AM   #4
Bart B.
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What you have may be a normal situation with loads having pressure too far below minimum.

When the firing pin strikes the primer with a normal max load, it drives the case hard into the shoulder setting it back a few thousandths. When the primer fires, the powder burns and expands the case starting at the shoulder then working back. This pushes out the primer so it stops against the bolt face then stretches the case back until the case head stops against the bolt face pushing the primer back into the case flush with its head.

I don't think the load used has enough pressure to do this. That's why the primers are sticking out of the case a few thousandths. Your barrel's bore and groove diameters may be way too big.

One exception to the above. . .the primer cup is extruding into the firing pin hole in the bolt face and a crater is formed with its outside edges above the rest of the fired primer's flat surface. This happens when the hole in the bolt face is is too big for the firing pin's tip diameter. Use a magnifying glass to check this.
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Old April 11, 2013, 01:19 PM   #5
mehavey
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Quote:
"...shot 120 rounds of factory Ammo (140 GN) and upon measuring the fired
brass I noticed every primer was pushed out ..."
Normally, factory ammunition is loaded "warm," so protruded primer would definitely be unusual there from low pressure.

What was your handload recipe/bullet/powder/weight, etc?
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