Richard Lee's 2nd edition "Modern Reloading"

by brionic , Tuesday, September 03, 2013, 22:01 (4103 days ago) @ Fowler

contains a neat section on reduced loads, with cast and jacketed.

He provides technical info on the how and why, and specific loads for 30-30, .308, and 30-06. Beyond that, he provides "pressure factors" for specific loads with particular powders, and a formula for how to determine your own reductions. The pressure factor is a decimal that allows you to calculate either pressure or velocity reduction for every 1.0 grain powder reduction.

For Varget, with a jacketed 140 gr bullet, the pressure factor is .979. Using the maximum velocity of 2772 fps/43.7 gr Varget, multiplied by .979 for every grain reduction, it appears that a 12 gr reduction of the maximum load would yield a velocity of 2,150 fps.

Other powders that include pressure factors for the 140 grn are H450, H380, H4831, H4350, H414, and H4895.

Don't take my word for it, though. The book is a good read, and is worth the price.

I can scan the pages if you are interested, but the explanation on bullet pressure and how to perform the calculations bear reading.