Thread: Signs of pressure in a 6.4x47

I'm not sure I completely agree with @Dermastor comment above.

Diminishing increase in velocity is also an indication of a node. In a full spectrum of loads there are several of these as you progres thru increasing powder charges. If you stop below the first zone of diminished velocity increase, you may still be well below max....

Flat primers to me are often more a sign of poor head spacing on the case rather than pressure.

The 2 things I look for in terms of pressure are heavier bolt lift and marks on the case base. Without fail,me very single hot load I've had, has had extractor/ejector marks.

Thanks Guys, some useful information.

Originally Posted by ebf

I'm not sure I completely agree with Dermastor's comment above.

Diminishing increase in velocity is also an indication of a node. In a full spectrum of loads there are several of these as you progres thru increasing powder charges. If you stop below the first zone of diminished velocity increase, you may still be well below max....

This is a great topic and now that we have grown tired of discussing ladders, OBT, OCW, and 3-shot groups, doesn't this deserve its own thread at some stage?

Originally Posted by ebf

Flat primers to me are often more a sign of poor head spacing on the case rather than pressure.

+1. I think most would find the edges do start to progressively square up though as loads are ramped, but with a good case-chamber fit then like yourself I've also found other pressure signs show up before full-on flattening. If things have been pushed to the stage where the head is just a smooth surface with a colour change then I can't help but feel that other indications would have been neglected long prior. Interestingly I can get slight but squashed looking cratering from moderate loads upwards from the pockets in the Lapua being slightly deeper than the CCI450 primers - a similar effect also caused by the primer having room to move during firing.

Originally Posted by ebf

The 2 things I look for in terms of pressure are heavier bolt lift and marks on the case base. Without fail,me very single hot load I've had, has had extractor/ejector marks.

Now I have to question this. Are you honestly trying to convince us that you have only ever fired off one hot load ? I bet it was in that rear-locking thing you owned too.

Originally Posted by ebf

@Puffin, putting a 6.5 projectile in a 6.4 chamber WILL cause a pressure spike
Sorry dude, couldn't resist. Catch you at the range sometime, my bloody swipe card has stopped working, aargh !

I fixed that up really quickly! You are either a true forum junkie or stalking my threads.

Originally Posted by ebf

The 2 things I look for in terms of pressure are heavier bolt lift and marks on the case base. Without fail,me very single hot load I've had, has had extractor/ejector marks.

Originally Posted by Puffin

Now I have to question this. Are you honestly trying to convince us that you have only ever fired off one hot load ? I bet it was in that rear-locking thing you owned too.

Finger trouble typing on the iPad. Meant to say "every single hot load", of which there have been several Funny thing is I can't remember any out of the 788.

Originally Posted by ebf

Finger trouble typing on the iPad. Meant to say "every single hot load", of which there have been several Funny thing is I can't remember any out of the 788.

The brain has a tendency to discard the bad shit and remember the good ..


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