As with Ackley's findings, I-too, in my meager testing of similar cases, have found that straight-walled cases, ie: those with minimal case taper, produce much less bolt thrust than do more tapered cases. This stands to reason and Ackley's thoery of the case walls cripping the chamber walls in correct here.
; The big question here is what constitutes minumum case taper. My .375/06IIMP has only .005" per side while the .257 Ack IMp, and original .375/06IMP I had, both had .0075" per side, taper.
; All of these rounds, including a 9.3x62, with .010" taper per side, all exhibit incredible ballistics with no noticable bolt thrust, whereas similar case capacities but with more tapered cases, fail to produce those ballistics due to the bolt lockng up from thrust.
; Most of the 'straight-sided' cases, indeed have much more taper than these expamples and therefore develop greater bolt thrust.
; I have found that an improved-type case with a gentle, 20 degree shoudler angle gave ballstics identical to the same capacity case with sharp, 35 degree shoulder, so the shoulder itself actually has little to do with bolt thrust. Case in point was my .260 CLC compared to the 6.5/.284- identical capacities, but very much different shoulders, with case shape, ie: taper, almost identical.
; Tom - the slower the powder, the longer the pressure curve - of course. Also- the further down the tube the pressure remains higher. It should be noted, in shotshells, shotgun powder is used. This powder is quite fast compared to rifle powders(obviously), and it can also used in some handguns.
; As to recoil comparrisons - in order to duplicate the ballistics of Reloader 15 with H4931 - you will need about 15% MORE (or more) of the slower powder - therefore it kicks more - the more you burn, the more it kicks.
; Shoot identical amounts of H4831 and Reloader #15, and the slower powder will kick less - due to it's reduced pressure and velocity. There is a cross-over point just above the RE#15 load, where steadily increasing the 4831 will begin to kick more. I'm not a physisist can't even spell it - but, I know what kicks and what doesn't. BTW- you can use shotshell powders in a 12 bore double, that will give you exits on side brain shots on Indian elephants, with cast round balls. These loads duplicate the old 7 dram heavy load.