We present the preceding Accurate Arms Study here to give the reader a feel of the real-world effects of primer changes in typical rifle cartridge loads and for one other important reason. One would hope that the results of this very careful study would do one thing – suggest to the prudent reader that anyone believing they can predict,a priori, pressure, consistency or velocity consequences of any particular primer substitution in any particular load is, more often that not, bound to be very much surprised.
Unusual Loads Give Unusual Data
One
possible conclusion one might make in response to evidence from unusual
revolver loads, where increasing charge mass in an already highly-compressed
loading, tends to decrease both peak chamber pressure and velocity,
is that increasing charge volume might always increase boiler room
pressurization in response to primer blast. If this were true, increasing
charge mass in any loading would always result in greater pre-ignition
bullet movement (if any occurred) and hence increased pre-ignition
boiler room volume so that, depending upon degree of charge increase
and rate of charge combustion, peak pressure might increase, decrease
of remain constant. However, this example is misleading: Charge
in such loads is so highly compressed that significant elastic force
is transmitted from deformed propellant granules to bullet base; hence, increasing
charge, progressively lessens primer impulse required to initiate
any given amount of bullet movement – all else being equal, a heavier
charge generates more primer-induced bullet movement even if effective
primer