7mm PRC Factory Hornady ammo issue

What im trying to explain is i dont believe they are over pressure. Yes the brass is smoked, but thats only one piece of a much larger puzzle and theres alot of other factors that suggest it may not be overpressure.

1 = Powder charge ( in my instance ) is well below book max across 2 different data sources.
2 = I have been 1.5gr higher in powder charge (to book max) before starting to see press on other hornady brass that isnt showing press on the first firing. ( And that brass is still happy 3 firings later)
3 = MV is in line with suggested MV vs Charge Data
4 = MV is consistent across brass that shows pressure vs not. All else being same (powder type / primer etc) then how is the brass from the 2nd shot of my 3 shot group showing "overpressure" yet the MV ES is 7fps across the group, & 80fps lower than what i have previously found pressure at. MV is a direct result of pressure so if the 2nd shot was way over pressure, where is the velocity?

Yes things like oil in the chamber, temperature etc can all play a part but when you have a clean gun and fire 3 rounds back to back with identical loads, the ES is 7fps & the second shot shows pressure when the others dont, theres something else going on than just some "hot loads".

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Originally Posted by 6.5 CRD

What im trying to explain is i dont believe they are over pressure. Yes the brass is smoked, but thats only one piece of a much larger puzzle and theres alot of other factors that suggest it may not be overpressure.

1 = Powder charge ( in my instance ) is well below book max across 2 different data sources.
2 = I have been 1.5gr higher in powder charge (to book max) before starting to see press on other hornady brass that isnt showing press on the first firing. ( And that brass is still happy 3 firings later)
3 = MV is in line with suggested MV vs Charge Data
4 = MV is consistent across brass that shows pressure vs not. All else being same (powder type / primer etc) then how is the brass from the 2nd shot of my 3 shot group showing "overpressure" yet the MV ES is 7fps across the group, & 80fps lower than what i have previously found pressure at. MV is a direct result of pressure so if the 2nd shot was way over pressure, where is the velocity?

Yes things like oil in the chamber, temperature etc can all play a part but when you have a clean gun and fire 3 rounds back to back with identical loads, the ES is 7fps & the second shot shows pressure when the others dont, theres something else going on than just some "hot loads".

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Yep make sens yet these cases must slam hard against the bolt to have bolt face stamped in it which isn’t really something you want

any chance that the problem brass are thicker (so heavier) and could be same powder charge less space situation?

be good to know why the brass is acting up whether it be a inconsistency in neck thickness or somewhere else

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Originally Posted by Bill999

any chance that the problem brass are thicker (so heavier) and could be same powder charge less space situation?

be good to know why the brass is acting up whether it be a inconsistency in neck thickness or somewhere else

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If the brass was thicker or had less capacity than the others, would mean more pressure for the same powder charge. But this would show in the velocity & it doesnt.

I have read somewhere you can get ejector and bolt face marks from oily chamber or oil/lube left on case. Will try to find this paper again, the guy was explaining it is a misconception oil in chamber or lube left on case increase pressure, he did some test with chrono showing no increase in speed but marked cases and heavy bolt. Rather than increased pressure he said it is the case not being able to grip on the chamber causing the case to slam backward in the bolt face.

Not sure if what this guy said is correct and if it is what happen here for some reason. It doesn’t really explain loose primer pocket. Maybe it is just softer brass

Yeah i have read that too. I always make sure my rifles are clean before use, i use a bore guide when cleaning and a chamber mop to make sure chamber is clean & clear. Definately wasnt anything foreign on any of my cases either.

Here is another one… boxes I shot had a compressed load, all from same batch. We checked boxes from a newer batch and load is not compressed so less powder or most likely different powder as it sounds like a lot less.

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Originally Posted by tibo

Here is another one… boxes I shot had a compressed load, all from same batch. We checked boxes from a newer batch and load is not compressed so less powder or most likely different powder as it sounds like a lot less.

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Yeah hornady used 3 different powders with the Prc match ammo.

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seen the same thing 2-3 years ago with hornady .308 superpreformance in a buddies brand spanking new top end rifle.... similar numbers of failures and similar results on brass and it was completely random as to when in shot string it would occur..and they FELT and SOUNDED hot even through reasonably heavy rifle with suppressor fitted.
put me right off that sort of ammunition completely

I remember hearing that because of the component shortages the ammo manufacturers are doing a lot of trading for what they need with each other which leads to a fair bit of inconsistency. I wonder if this is related somehow?

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Originally Posted by ElDax

I remember hearing that because of the component shortages the ammo manufacturers are doing a lot of trading for what they need with each other which leads to a fair bit of inconsistency. I wonder if this is related somehow?

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Thats why you need to cheek your zero between batches of ammo.

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Originally Posted by 6.5 CRD

Shooting them. Heres a picture from yesterday showing what i mean. 3 shot group from left to right with the same below max powder charge, same seating depth, 2932fps average, ES of 7fps. I have been to 3008fps with another 1.5gr of powder & not seen pressure signs on some of my other hornady brass.

As you can see all the primers look roughly "the same amount of flat" for lack of a better term. As above MV showed the 2nd shot to be the same speed as the rest, yet bolt was hard to lift & as you can see the brass is done. Just deprimed them, Shot 1 & 3 the primers still snug, shot 2 which is showing all the "pressure" the primer pocket is gone, primer almost fell out.

Attachment 227696

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Hard to tell from this image, but those primers don't look to be what id call flat. Could just be a bad image.
If the primers aren't really flat, and velocity is within spec, then its probably unusually soft brass.

Can get the case slamming back with excessive headspace causing big swipe marks, but that doesn’t explain loose primer

The guys in the US are having the same issues

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Originally Posted by PerazziSC3

Can get the case slamming back with excessive headspace causing big swipe marks, but that doesn’t explain loose primer

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yeah blew the primer and the back plastic shroud off my bolt due to poor brass prep
was rather loud in the face area,