I'd look at bushings for sure
VV N140 temp sensitivity
- Thread starter Dave M.
- Start date
If I were to pursue the load further than yes I would.
When I run out of H4895 I’ll be using N140 and Varget for sure.
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jxb
Gold $$ Contributor
It's old (2012), but here's some you all might find of interest. Scroll down...
for those that don't click on links, go to hodgdon dot com which will redirect you to that site, then resources at the top and choose reference data left side under information. Why they don't put everything including their reloading data page under one site is beyond me and definitely annoying. shop.hodgdon.com has a link at the top to hodgdonreloading.com but I've never found it on hodgdon.com-->hodgdonpowderco.com
Would be super nice if all the manufacturers provided updated/current data for at least their products that are labelled as temp insensitive. There's certainly enough volume sold to justify the time and cost.
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Mulligan
Silver $$ Contributor
If Hodgdon believes that bull squirt, they are dumb enough to drink their own bath water! H4895 is NOT any more “stable” than N -140 or N-135 in my testing.
CW
Mulligan
Silver $$ Contributor
is CUP pressure measurement?
Copper units of pressure or CUP, and the related lead units of pressure or LUP, are terms applied to pressure measurements used in the field of internal ballistics for the estimation of chamber pressures in firearms.
CUP is a special unit of measure defined only for ballistic testing; psi is a standard unit of measure for all pressure testing in the English system. Whether you are testing radiator caps or valves for a nuclear submarine, psi is the same. CUP has no other use
The results of a very quick search……there may be more to the story???
CW
I seem to recall H4895 going up a bit more than 6 f/s during summer months that didn’t reach 125 F
Moving forward having a decent chronograph now i’ll be able to keep track of these little details a bit easier.
Shot great is South Africa in 93 to 98 degrees. Yes the speed increases, but it's not stupid peaky on the pressure.
One variable I've not seen mentioned is a difference in case volume, for example from 308 to a 223.
You might see more difference in a 24 grain 223 load at 0 degrees C vs 30 degrees C, than you would in a 45 grain 308 load under a similar range of conditions.
My recent experience with N140 has been that I had to adjust my 223 load when the temperature dropped over the winter months. The velocity changed enough that it fell out of tune, at least 30-40 fps less than it produced in the summer months.
As with all things 223, it didn't take much to make a difference.
I do know that a small volume case is more sensitive to minor charge weight changes than a larger case, but does that sensitivity include changes in temperature as well?
You might see more difference in a 24 grain 223 load at 0 degrees C vs 30 degrees C, than you would in a 45 grain 308 load under a similar range of conditions.
My recent experience with N140 has been that I had to adjust my 223 load when the temperature dropped over the winter months. The velocity changed enough that it fell out of tune, at least 30-40 fps less than it produced in the summer months.
As with all things 223, it didn't take much to make a difference.
I do know that a small volume case is more sensitive to minor charge weight changes than a larger case, but does that sensitivity include changes in temperature as well?
Copper Units of Pressure
Basically a piston gets forced against a copper disk of know dimensions and firmness and you measure the permanent deformation made by the shot.
No known method of converting to something actually usable for comparison or mathematical manipulation - ie can not convert to PSI or any other standard unit.
Murray Brook
Silver $$ Contributor
CUP ↔ PSI Calculator - Calculator Academy
Enter the total CUP into the calculator to determine the equivalent PSI.
calculator.academy
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