I was wondering if you guys have noticed this happens too? Cartridges with more power then the 30-06 class tend to flatten out the primers more, even with factory ammo. I have a lot of 338 Win mag. brass from factory ammo that I've saved for reloading and it all has flattened primers. I picked up 270 WSM, 7mm Rem. Mag., 300 Win. Mag. discarded brass at the range where people sight in their rifles before hunting season and all of it has flattened primers.
Magnum rifles and flattened primers
- Thread starter CZ_Brno
- Start date
In my experience, flattened primers are not a terribly good sign of anything. It doesn't take much to flatten primers, a slightly worn or loose primer pocket is all it really takes, even with entirely normal charges. If they are reloads with reamed pockets, it would not be at all suprising to find flattened primers.
paperslayer
Regular
- Location
- Chilliwack
what almost defines a magnum cartridge is the enormous pressure many are over 60,000psi versus the 30-06, where pressures run between 39,000psi and 45,000psi One of the frustrating realities of reloading magnum cartridges is that really good brass does not exist. Winchester and federal brass is crap and is only good for a handfull of reloads before the primers fall out. The culprit is the pressures. If you are reloading and getting flattened primers, you need to throttle back. It is a sign of excessive pressure. Significant cratering of the piring pin strike is also concerning, and stick bolt lift too. Depending on chamber tolerances, it is possible to have excessive pressure with factory ammo. Light bullets in tight twists cause excessive pressure too.
@paperslayer
The .30-06's rated max pressure is 60,200psi. Most load data I have looked at only reaches around 59,000psi though.
Of course as you said chamber tolerances and other factors effect what pressure is reached, when.
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@CZ_Brno
Primers will flatten at a certain pressure regardless of what the maximum rated pressure of a cartridge is. If you are looking for flattened primers in, say, a .45-70 case then you will practically have to make a pipe bomb before you will get flattened primers. The thickness of the primer cup also plays a huge role in flattened primers. I've never seen a fired Federal primer that isn't flattened to matter what the pressure was. CCI primers seem to be more resistant to flattening and wont flatten totally even in my near max loads in .300 Win Mag. What brand where the cases you picked up at the range that had flattened primers? If they are Federal it's not a good sign of anything. Regardless most magnum cartridges go above 60,000psi like paperslayer said so are far more likely to flatten primers. As Moose308 said flattened primers aren't a good sign of anything (except in comparison to another load with the same components but a different powder charge.)
Firing pin strike craters can be caused by overpressure or by a weak firing pin spring or by excessive space around the firing pin in the bolt face.
A sticky bolt lift/case extraction can be caused by overly soft brass below maximum pressure. Hornady ammo is known for being bad for this.
The .30-06's rated max pressure is 60,200psi. Most load data I have looked at only reaches around 59,000psi though.
Of course as you said chamber tolerances and other factors effect what pressure is reached, when.
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@CZ_Brno
Primers will flatten at a certain pressure regardless of what the maximum rated pressure of a cartridge is. If you are looking for flattened primers in, say, a .45-70 case then you will practically have to make a pipe bomb before you will get flattened primers. The thickness of the primer cup also plays a huge role in flattened primers. I've never seen a fired Federal primer that isn't flattened to matter what the pressure was. CCI primers seem to be more resistant to flattening and wont flatten totally even in my near max loads in .300 Win Mag. What brand where the cases you picked up at the range that had flattened primers? If they are Federal it's not a good sign of anything. Regardless most magnum cartridges go above 60,000psi like paperslayer said so are far more likely to flatten primers. As Moose308 said flattened primers aren't a good sign of anything (except in comparison to another load with the same components but a different powder charge.)
Firing pin strike craters can be caused by overpressure or by a weak firing pin spring or by excessive space around the firing pin in the bolt face.
A sticky bolt lift/case extraction can be caused by overly soft brass below maximum pressure. Hornady ammo is known for being bad for this.
