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Flattened Primers

 
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  #8  
Old 11-09-2012, 09:40 PM
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Re: Flattened Primers

Do I have to resize the entire neck? Or should I just buy a neck sizing die to make things easier and less confusing
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  #9  
Old 11-10-2012, 02:41 AM
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Join Date: Jun 2005
Posts: 159
Re: Flattened Primers

I have a rem 700 in 257 bee. It shows cratered primers no matter what the load... poor firing pin fit dimensions by Rem... I learned to ignore it. I use a chronograph so I know when I'm up to snuff in velocity... But I don't push it... There's no free lunch.
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  #10  
Old 11-10-2012, 03:55 AM
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Re: Flattened Primers

I don't have cratered primers they are ust flattened. I think I'm going to pick up a neck sizing die. This way the shoulder won't get resized
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  #11  
Old 11-10-2012, 09:02 AM
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Join Date: Aug 2008
Posts: 65
Re: Flattened Primers

I used to get the flattened primers all the time, same as you, no craters just flattened.
I just accepted it, I had no other pressure signs at all. If accuracy was good, I used the load. I switched to neck sizing dies, and honestly couldn't see any improvements in accuracy or the primer issue.
I then heard a target shooter talking about reloading, and he spoke about neck sizing, should/can only be done 1-2 times before full length resizing, because as the brass flows to the shoulder area, neck sizing only will start to allow the shoulder to require jamming on bolt closure. This causes inconsistent neck tensions and hurts accuracy. Something I had noticed, after a few loadings the groups would start to open up.
So I searched online for a Headspace Gauge, that could be used for multiple calibers, and found this one.
w ww.larrywillis.com/
I couldn't be happier with the gauge, you simply measure the shoulder of a fired case, and adjust your full length die until you are bumping the shoulder back the desired amount. (.001")
This insures you are sizing your brass to your chamber.

Improper head spacing the way I understand anyways allows the case to move forward to contact at the shoulder when the firing pin strikes, then there is room between the case and the bolt face, which as the powder ignites the primer actually pushes out of the case to contact the bolt face before the brass stretches to take up the gap, which crushed the primer. This is one of the causes of flat primers, even without too much pressure.
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  #12  
Old 11-10-2012, 01:41 PM
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Join Date: Jun 2010
Location: greenwood, IN
Posts: 3,600
Re: Flattened Primers

read the thread again, and there's some interesting points being made. Over the years I have seen two rifles that came from the factory with a "dish" in the bolt head. Not much, but three or four thousandths dish in them. Being as the original poster has taken his rifle to someone that knows his business (Hart), we have to assume that the chamber is to spec because they said it was. That brings us back to square one again.

Normally a flattened primer is a sign of a few things happening after initial ignition of the primer:
1. Excessive pressures
2. loose primer pockets
3. with reference to excessive pressures, has the loader actually did an accurate inspection of the cases after firing? Could the grip on the bullet be excessively tight? Maybe one hell of a doughnut in the base of the neck? Or maybe the neck has expanded to the point that it is less than .0025" smaller than the chamber neck?

I have seen the wrong powder dumped in a bottle from the factory a couple times, but this is very rare and was easilly noticeable in the cases I saw. His loads are far enough down the load scale that even his measurer would still be in a safe range, so I think we can forget that as well.

Is it possible that the throat is so contaminated that it's causing a pressure spike? Is the chamber actually inline with the bore and also concentric with the bore. (I have seen this more than once)

Try this check:
lay a strip of masking tape along the barrel lengthwise. Run a very tight patch (lubed) thru the barrel with a good quality jag (I prefer Proshot). Mark on the tape the locations of the tight spots and where it loosens up. If you happen to start out with a very tight place in the area just after the throat you may have a problem. I have seen burrs left from reaming the chambers here, and that will cause an excessive pressure spike. You can take the further by "slugging" the barrel.
gary
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  #13  
Old 11-10-2012, 02:23 PM
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Join Date: Nov 2012
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Re: Flattened Primers

If the chamber was not in line wouldn't i see this effect accuracy? As of now I get 1.75 - 2 inch groups at 200 yards. And this is without really tweaking my loads. I shot a couple loads with 67 grains of IMr 4350 which is at the higher end of load and I still got flat primers as expected. I was also expecting heavy bolt lift which I did not. So do I dare to just except the flat primers and have fun shooting?
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  #14  
Old 11-10-2012, 03:08 PM
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Join Date: Jun 2010
Location: greenwood, IN
Posts: 3,600
Re: Flattened Primers

Quote:
Originally Posted by tweek1142 View Post
If the chamber was not in line wouldn't i see this effect accuracy? As of now I get 1.75 - 2 inch groups at 200 yards. And this is without really tweaking my loads. I shot a couple loads with 67 grains of IMr 4350 which is at the higher end of load and I still got flat primers as expected. I was also expecting heavy bolt lift which I did not. So do I dare to just except the flat primers and have fun shooting?
with 2" groups at 200 yards, I'd guess your chamber is strait. Have you measured the primer pockets?
gary
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