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Neck turning and Blown primers

 
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  #8  
Old 05-03-2014, 11:42 AM
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Re: Neck turning and Blown primers

I was not referring to headspace but OA case length. Often times when pulling the expander ball back through the case neck, they stretch.
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  #9  
Old 05-03-2014, 12:41 PM
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Re: Neck turning and Blown primers

Over all case length is .005 under book trim length and within .001 over the entir batch.
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  #10  
Old 05-03-2014, 02:34 PM
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Re: Neck turning and Blown primers

Based on everything you said you've already checked, and if you've heeded the possible culprits already identified in this Thread - the likely possibility is that your powder is now creating increased pressure. It's not unheard of for a new Lot of the same Brand of powder to yield higher or lower pressure than a previous lot. Also need to double and triple check you powder scale (balance beam or digital) is calibrated correctly.

If they're still chambering tight, you ought to make absolutely sure your case necks aren't being pinched/wedged along the neck of the case, where the chamber might be trying to swage the neck w/seated bullet into too narrow of a chamber neck diameter. This comes back to the possibility of a donut formed inside the case neck, the case necks being too long, a batch of overdiameter bullets, or anything else that could cause the outside diameter of the loaded cartridge case neck to be too large in diameter to fit into the chamber neck.

Measure the OD of the neck of some of your loaded cases and see if there's any measureable difference. You said you've fired these cases a number of times. The thickness of the case neck will typically increase at the case shoulder/case neck with repeated firings.

Last thing I've read about, but never experienced since I don't shoot enough between cleanings to experience it, is to make sure a carbon ring isn't forming in the bore just ahead of the case neck.

But you said you just changed to a new can/Lot of powder, so I think you're overlooking the most obvious potential culprit - unless your casings still chamber with difficulty.

Let us know what your finally conclusions are? Always look forward to learning from others' experiences.

PS: Believe it or not, I just measured some 7mm bullets that measure 0.282" in outer diameter. They slid into my prepped case necks too easily so I began measuring things.
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  #11  
Old 05-03-2014, 07:16 PM
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Re: Neck turning and Blown primers

As for the donut. One is not discern able and the ID reamer in the neck turning operation is supposed to elevate one if present. It did not appear to be cutting any material. The dropping a bullet into the fired case method is a no go. If a fella desired he could have taken these fired cases, reprimed, recharged them and loaded them. The neck was tight enough that post firing/ post spring back it was just as tight as initial bullet seating. Hence the neck turning. Post neck turning and firing bullet bearing surface will still not enter neck of case without pressing it.
__________________
An unarmed man can only flee from Evil and Evil is not overcome by fleeing it.

The proper use of a Pistol is to fight your way back to where you left your Rifle.

The best gun to have? ... The one in your hand when the fight starts!

Respect All - Fear None
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  #12  
Old 05-03-2014, 07:59 PM
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Re: Neck turning and Blown primers

I have measured every dimension I could think of on fired cases, loaded cases and cases prepped to be loaded. I have no method to measure variances in powder but the one thing I have found is post bullet seating a slight increase (0-2 thousandths) in diameter on some of the cases at the case body/ shoulder junction. This brings my seating die setting into question. In my opinion. I did not consciously change it. And don't recall it being loose at any point but a lot has occurred since now and originally setting it. Could it be possible I was getting some unintentional crimp along with a little crush on the case in the seating operation and causing some pressure?


It will be a bit before I can fire some rounds and have solid conclusions.
I do want to mention I appreciate y'all's help and insight. It really helps. There is A LOT going on in this quest for 1000 yard accuracy .
__________________
An unarmed man can only flee from Evil and Evil is not overcome by fleeing it.

The proper use of a Pistol is to fight your way back to where you left your Rifle.

The best gun to have? ... The one in your hand when the fight starts!

Respect All - Fear None
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  #13  
Old 05-03-2014, 10:08 PM
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Re: Neck turning and Blown primers

Considering all the work investigating the chamber/ case fit you've done my suspicion is that new can of powder. I once bought 4 cans of WW 680BR from a store that was closing in CA and then moved to Idaho. Didn't open the cans for about 5 years but when I did I found they contained a mix of powders, one of them being something with color dyed flakes in it. WW 680BR is a Ball Powder! That was four cans of fertilizer!

Check the powder. Twice. You pretty much ruled out the other stuff.

KB
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  #14  
Old 05-03-2014, 10:32 PM
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Re: Neck turning and Blown primers

You changed powder lot and primer lot and you are loaded at high pressures to start with. So that is always a risk to get a change in acceptable pressure levels. You were just unlucky that the new powder lot is faster and the new primers softer and the temp on the day may have been higher than usual .
Staying down in pressure closer to reccomended levels tends to take account of many of these kind of lot variations .
Neck turning for a factory chamber in this instance can't raise pressures . I have never seen that happen .
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