Thread: Over pressure signs ??

Fired my first vmax 53 out of the 223 yesterday.

Looked at the bolt face and it had a dirty ring around the firing pin
Then I looked at the fired case (left in picture ) and compared to a fired case from a vmax 40 load (right in picture)

The primer looks pretty flattened to me .. Definite signs of over pressure to me.

Opinions ?

Tim

Naa Tim, that's not a flat primer.

Also, cratered primer and/or extractor mark is IMHO a better indicator of pressure. Flat primers can often be a sign of headspace rather than hot load.

Was bolt lift sticky or normal ?

Tim

Both primers look ok to me.

I don't see any obvious signs of over pressure that would concern me at this stage.

Primer on the left still has a visible radius and no sign of cratering around the firing pin strike.

Was there any other signs of over pressure, like sticky bolt on opening or difficulty extracting the case from the chamber?

I'll post some pics later with examples of flattened and cratered primers that while up in pressure were not causing problems otherwise.

The darkened ring around your firing pin hole on the bolt face may be due to a loose primer leaking rather than over pressure.

Cheers
Pete

Normal

Sweet. I'll proceed on track with caution then.

Thanks guys

Tim

Below are three rounds with various degrees of flattened primers, all are hot loads yet all perform well in the Rifles they were loaded for with no other signs of over pressure.


This Norma .243 also has a very flattened and cratered primer and as can be seen from the profile view it also has a serious case of Head Separation.
This was caused by a head space issue.


Hope this helps.

Cheers
Pete

Wow P38 that 243 case would make the arse clinch up a bit

Originally Posted by BRADS

Wow P38 that 243 case would make the arse clinch up a bit

It did Brads

Fortunately it wasn't mine and I was observing from a safe distance.

Cheers
Pete

Case head separation is also (if not mainly) caused by too dry a chamber and case. The case needs to be able to 'creep' on the chamber walls to be able to spread the load evenly over the length of the case. That way nearly 10% of the thrust is carried by the case itself. If too dry/rough the case does not creep and the head starts to separate at which point the full thrust is transferred onto the bolt face. Without excess headspace this would take several firings to manifest if at all.

Full length sizing is a major culprit too.

Originally Posted by 303Guy

Case head separation is also (if not mainly) caused by too dry a chamber and case. The case needs to be able to 'creep' on the chamber walls to be able to spread the load evenly over the length of the case. That way nearly 10% of the thrust is carried by the case itself. If too dry/rough the case does not creep and the head starts to separate at which point the full thrust is transferred onto the bolt face. Without excess headspace this would take several firings to manifest if at all.

Full length sizing is a major culprit too.

If done incorrectly, if done properly there is no reason for it to cause case head separation at all.

Yup. I should have said 'over sizing'.

Those primers look ok to me.

Below are the worst I got in developing the 223Maximus. This was a 60gr bullet doing 3640fps, it felt fast when firing and I went home after that and took the rest apart.

Also, I didn't need to decap this one, the primer fell out after removing the case from the bolt face. It is not meant to be a rimmed case either.

hehe, "not meant to be a rimmed case"

I had a case that looked the same, definitely puts the shits up you huh. Only one out of 60 that did it.

Very good Pics there P38, thanks for posting those.