Flat primer?

[muleman69]

Shot 9 rounds and noticed one primer flatter than others? All components being equal and all powder hand weight? Rounds were on the light /mild side ,barrel not hot and cool day. Round was not last out of barrel . Barrel and chamber clean. The primer was flat enough to call it a pressure spike for sure

 

[FatOldMIHunter]

I see question marks, but I see no question there. If it is just one out of many, I would suspect either a slightly loose primer pocket or a randomly softer primer or as you said, a pressure spike, possibly from improper powder measurement, an overly long case, excessive neck tenson, abnormally thick brass, etc.

 

[Rsadams]

Kind of primer , what caliber..

 

[retired]

and just what sorting was done to the cases...my guess it is heavier...
or did you use a beam scale to weigh your powder ?

 

[onelastshot]

101 different possibilities that would result in a flat primer; anything from miscalculation in powder charge to a soft primer or a loose one as well as case volume being different. Were they all the same type of brass? were you using a auto digital scale or standard? Some brass will have case volumes that very and will cause a spike in pressure also, a bullet jammed into the lands can cause spikes in pressure.

 

[Immike]

I write on my cases with a permanent marker that have any anomaly to see if it happens again.

 

[Zero333]

Primers alone can lie.

many different possibilities, and pressure is just one of them. I would not worry too much.

Shoulder bumped too much will cause flat primer.

Soft primer cup will cause flat primer.

Primer seated too much below flush will cause flat primer.

Was the bolt lift heavier ?

Can you see a half moon or full moon ejector imprint on the case head ?

If you answer NO to those 2 questions then you have no pressure problems.

 

[searcher]

Because you were so careful about the powder and other attributes of loading, I'm thinking it was an "over-bumped" shoulder, a common cause of the flattened primer, as Zero333 listed. Measure the base-to-shoulder measurement against the fired cases with the normal primers. If it is shorter than the others when loaded, as they seldom fully blow out when they slam rearward like that, it may indicate that as a strong candidate. Also, if you had sonic cleaned your brass or annealed, then drench/polished prior to loading, possible blob of tumbler media was in case prior to charging if you ran in media before fully dry.

 

[muleman69]

Kind of primer , what caliber..

210m .....7mm/08

 

[muleman69]

I see question marks, but I see no question there. If it is just one out of many, I would suspect either a slightly loose primer pocket or a randomly softer primer or as you said, a pressure spike, possibly from improper powder measurement, an overly long case, excessive neck tenson, abnormally thick brass, etc.

Maybe neck tension, everything else was equal to my knowledge.I turned the necks and will end up with .001 tension this go. We shall see

 

[muleman69]

and just what sorting was done to the cases...my guess it is heavier...
or did you use a beam scale to weigh your powder ?

Didgitel scale, Lapua brass, did not weight

 

[muleman69]

I write on my cases with a permanent marker that have any anomaly to see if it happens again.

Good idea ,wish I would have thought of that,I will next time for sure

 

[muleman69]

Primers alone can lie.

many different possibilities, and pressure is just one of them. I would not worry too much.

Shoulder bumped too much will cause flat primer.

Soft primer cup will cause flat primer.

Primer seated too much below flush will cause flat primer.

Was the bolt lift heavier ?

Can you see a half moon or full moon ejector imprint on the case head ?

If you answer NO to those 2 questions then you have no pressure problems.

This was once shot lapua brass, pockets and primer seat looked good, bolt not heavy and no imprint. Shoulder bump could be an issue as I have been messing with that trying to get it right. I will keep better notes this time around

 

[muleman69]

101 different possibilities that would result in a flat primer; anything from miscalculation in powder charge to a soft primer or a loose one as well as case volume being different. Were they all the same type of brass? were you using a auto digital scale or standard? Some brass will have case volumes that very and will cause a spike in pressure also, a bullet jammed into the lands can cause spikes in pressure.

Same Lapua brass once shot,digital scale

 

[M-61]

Shoulder bump could be an issue as I have been messing with that trying to get it right.

As a target shooter only, not a hunter anymore, shoulder bump is not something that I concern myself with at all. If the cartridges chambers and the bolt closes normally (going to be a different feel if jamming) I'm not bumping anything. I've never found flattened primers to be a concern (providing I am not getting a hard bolt LIFT) nor cratered primers. I am not loading 7-08 but the stuff I load is not over max amounts listed a few years ago and always working my way up. Easy on cartridge brass like a 222 I have never bumped. Some may have 35 reloads on it. Lots that I load crater the primers and if I were concerned I'd get the bolts bushed.

 

[Bart B.]

Shoulder bumped too much will cause flat primer.

How does that cause "flatter" primers?

How much is too much?

I ask because I've never heard of this before. And shooting rounds with about .010" spread in head clearance, all primers had the same shape.

 

[dickn52]

You can flatten them by applying too much pressure when setting them in a case not prepped right too. Using Mil Spec brass without removing the crimp can make them flatten.

 

[4xforfun]

You can flatten them by applying too much pressure when setting them in a case not prepped right too. Using Mil Spec brass without removing the crimp can make them flatten.

Read above posts ....brass is Lapua.

 

[Zero333]

How does that cause "flatter" primers?

How much is too much?

I ask because I've never heard of this before. And shooting rounds with about .010" spread in head clearance, all primers had the same shape.

I honestly dont know how much bump will cause flat primers but the idea is that the brass could slam against the bolt face.

 

[Bart B.]

I honestly dont know how much bump will cause flat primers but the idea is that the brass could slam against the bolt face.

The case head always slams against the bolt face reseating the primer that backed out a few thousandths before preasure peaked.

That's after the firing pin drives the case shoulder hard into the chamber shoulder so there's a couple thousandths or more case head clearance to the bolt face when the primer detonates. A few hundred psi in the case pushes the primer out a few thousandths then it stops against the bolt face.