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Presure signs question
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I need some help understanding signs of getting to much presure. I'm new to reloading and have read that flatening primers is a sign of high presure, how much flattening is exceptable if any because all of my primers seem to flaten to some extent?(even factory loads)
I am reloading for my 7mm08 using winchester brass, imr4064, sierra 120gr. prohunter and fed210m primers.
 
Posts: 3 | Registered: 13 July 2010Reply With Quote
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Primers are not a sure bet when it comes to reading pressures.Check the bolt lift with a factory load and reloads.
And work up to the max loads in any book.
Safe Shooting
 
Posts: 1371 | Location: Plains,TEXAS | Registered: 14 January 2008Reply With Quote
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Too often pressure signs singularly don't denote excess pressure. A flattened primer may be caused by a slight head space problem; a cratered firing pin strike can be a large pin hole in the face of the bolt; a heavy bolt lift can be a dirty chamber; etc.
It's when you have several of these come together that you should have a concern. Not to say that individual occurrences shouldn't be investigated.
Load books and a chrony and a awareness of the pressure signs should keep you on safe ground.


Aim for the exit hole
 
Posts: 4348 | Location: middle tenn | Registered: 09 December 2009Reply With Quote
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The bolt isn't hard to open after firing, it seems to open like it always has. The primers aren't completely flatened out to the point of filling the primer pocket or anything, they still have a slight rounded edge and no cratering around where the firing pin strikes the primer. just wanted to get some opinions from some of you guys who have been reloading more than i have.
 
Posts: 3 | Registered: 13 July 2010Reply With Quote
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I'm pretty much a novice at this myself rancher81 so most of what I'm going to say here was learned from this forum, and on a UK based forum as well.

I had a problem with my rifle in the sense that it totally destroyed primers on factory ammo, flat as a pancake almost every time. When I started into reloading I was posting on here because I was worried about what was going on with my reloads and the primers. Lots of folks on here told me that it was likely that my chamber was a tad on the long side and so my primers were backing out slightly and then being mashed when the case expanded to fit the chamber. I was able to convince myself that this was indeed what was happening because on some of my very modest pressure reloads it was possible to see that the primer was slightly backed out. So, flat primers might not be a sign of much at all.

I started neck sizing rather than full length sizing so my cases were a tight fit in the chamber and am now shooting stout loads with little or no signs of flat primers.

I will post some photos, many on here will have seen them before as I posted them when asking for advice but I hope they help you a little. It may also be that those much more experienced than I can provide much more information on what is happening in my photos but I will attempt to describe what is going on as best I can.

This is factory ammo fired in my rifle, you can see the primers are pretty much mashed:



Now, these are my reloads with a book minimum load and you can see that the primers are fine but that they have backed out a little. The load was "strong" enough to back the primer out but not "strong" enough to expand the case to fit the chamber:



These have been fired with a book max load which is giving me 3000fps in my 308W with a 150 grain bullet. As you can see the primers look pretty much like they did before firing and they are flush with the case head. These cases have been reloaded 7 times now with this load and the primers are still tight.

 
Posts: 442 | Registered: 14 May 2007Reply With Quote
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Hey Rancher81, I sent you a PM. tu2
 
Posts: 9920 | Location: Carolinas, USA | Registered: 22 April 2001Reply With Quote
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High pressure - Look for - Hard bolt lift-primer extruding into and around the firing pin- web area expanded as little as .0005"- shiny spot on head of brass from ejector. Photos here Link to photos.
 
Posts: 1295 | Location: USA | Registered: 21 May 2001Reply With Quote
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FWIW, those factory primers don't look "mashed flat" to me. I'd say they were quite acceptable.


Aim for the exit hole
 
Posts: 4348 | Location: middle tenn | Registered: 09 December 2009Reply With Quote
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Posts: 3 | Registered: 13 July 2010Reply With Quote
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As long as there is some definite radius on the primer edge you are fine, I see no evidence of pressure in the pix you have posted.
Flattened primers are just that, flat. The edges will appear "ironed" out to the pocket with a hairline gap between the primer and the case pocket.
You show a touch of cratering on a couple primers in your pictures that I would expect is due to a slightly large fireing pin hole or weak spring. Neither is really a problem normally. This is something you have to figure out by observing the brass from various loads over a bit of time. If they suddenly appear or are quite pronounced they can be sign of trouble, if they appear in all levels of pressure and are minor they are likely nothing to worry about, unless accompanied by flat edges on the primers.
Be aware too that low pressure can show very flat primers at times also. With low enough pressure the case is driven forward in the chamber and the primer backs out of the case slightly from pressure during ignition. The case then, as pressure rises some, is driven back against the bolt face "riveting" the primer and giving it the appearance of high pressure. Upping the charge a gr normally causes this to go away and primers to appear normal again.
Primers from what I`ve been told don`t start to excessively flatten until pressures exceed about 65K psi. If you see them you are very likely past the SAAMI spec for your cartridge. This is a reason too for not using them as a pressure sign in low pressure cartridges. A primer that will show no flattening in a 65K psi load from your 270 can not be a reliable gauge for judging where you are in your M96 Swede with a 50K psi pressure cap.


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Posts: 2535 | Location: Michigan | Registered: 20 January 2001Reply With Quote
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