out of the blue question when /where is peak pressure ?

C

CMaier

Guest
i have a buddy that believes peak pressure is about 12"
down the bbl, i say within 4 inch of bolt face.

use 6.5 creedmore to play with.
or
any other data you have
my answer is based off quickload.

his is off pressure trace readings of a 6.5 x55 swede.

another
"inquiring minds want to know"
 
I can't say with any certainty but, I would think there would be many variables including bore diameter and internal finish, case capacity, powder burn rate, primer, and bullet weight would all play roles.
 
My experience with Quickload is that the calculations are often very accurate as to projected velocities. I would tend to give enough credibility to the pressure chart to believe that it will be at least in the ballpark. What does Quickload project for the 6.5 X 55?
 
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i have a different view of quickload.
it is great software, but as with all things gun
there are lots of variables.
i keep a log of powder properties which vary from quickload
and use them when doing my powder workups.
same for case volume, and bullet length.

SGS said:
My experience with Quickload is that the calculations are often very accurate as to projected velocities. I would tend to give enough credibility to the pressure chart to believe that it will be at least in the ballpark. What does Quickload project for the 6.5 X 55?
Click to expand...
 
CMaier said:
i have a different view of quickload.
it is great software, but as with all things gun
there are lots of variables.
i keep a log of powder properties which vary from quickload
and use them when doing my powder workups.
same for case volume, and bullet length.
Click to expand...

Although I stated that I had found Quickload velocity predictions often to be surprisingly accurate, I have seen some cases that were pretty far off. I know that certain powders are notorious for large lot to lot variations, and as you said, there are lots of variables. Where I was going with this is that if you run a boatload of calculations with different cartridges and bullets, the shape of the pressure curve nearly always looks similar with peak velocity in the 2 to 4 inch range of bullet travel.
 
i agree.
i was looking to get statements to back me up..
cause..
he is using strain gauges and i was using someone else's software.
it was good to see similar numbers from others, and my buddy is coming around,
and now he has to figure out what his data actually is.

SGS said:
Although I stated that I had found Quickload velocity predictions often to be surprisingly accurate, I have seen some cases that were pretty far off. I know that certain powders are notorious for large lot to lot variations, and as you said, there are lots of variables. Where I was going with this is that if you run a boatload of calculations with different cartridges and bullets, the shape of the pressure curve nearly always looks similar with peak velocity in the 2 to 4 inch range of bullet travel.
Click to expand...
 
We usually find higher pressures at midcase than at casemouth. This is using Kistler 6215 gages and LabView. For midcase we drill the case and use grease to get true readings. The equipment is accurate enough to see the initial pressure spikes from the primer going off. This is with .223, .308, and .50BMG.
 
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