CUP or PSI

[338winmag]

How should one incorporate CUP or PSI information into their reload processing?

I noticed Hodgdon site specifies CUP for some of their Hodgdon powder but on the same site, IMR specifies PSI?

Any thoughts, comments or practices appreciated.

Thanks
338winmag

 

[DrMike]

There is not a precise correlation between CUP and PSI. Almost all reloading guides are transitioning to psi (or BAR) today as it is a more precise measure of pressure, and because it is actually simpler to measure. Those guides that still use CUP have simply not been updated. Within the next decade, I would expect all guides to be fully transitioned.

 

[338winmag]

I was hoping you would comment DrMike!

Do you incorporate any PSI data discernment into your reloading processes or is this data something only useful if one is reloading hot loads?

 

[DrMike]

For load development over which I have no control (after it leaves my loading bench), I make every effort to ensure that the loads are safe as verified by a laboratory. Consequently, I use the various manuals of bullet and powder manufacturers as I know they are pressure tested. Obviously, with the newer powders, this is not always possible. In these instances, I use QuickLoad and some years of experience to verify that I see no evidence of pressure in a load. I watch the readings on my chronograph, inspect the cases carefully both as I remove them from the chamber and after tumbling, and I consider the way a load acts given the conditions in which I am shooting. Some of the most dangerous loads I have shot were in "safe" rifles. Perhaps a chamber was cut a bit tight, or a lot of powder was excessively slow, or a lot of bullets were somewhat enlarged--I have witnessed all these situations. For my own loads, I tend not to run them hot. Consequently, I readily get ten or more loadings from a lot of brass, after which it is discarded.