Originally Posted by
TurnipEaterDown
I have had a question on this for a while now......................
What I would like to understand is: (1) is the formula is valid for lead (having used properties for lead), and (2) if the correct material property values for alloy compositions were available (recognized: not easy w/ variable compositions), would the formula work when bullets were made of alloyed lead?
My thoughts always go to permanent distortion (bending) of the base from combustion pressure, and buckling of the column interior to the lube groove(s). The reduced OD "column" interior to the lube groove acts as a connecting rod between what is effectively a piston (base band) and the body, and would be susceptible to buckling. Granted that any potential for column buckling of this section interior to the lube groove has to be considered in light of the lube becoming pressurized in the groove and acting as support that would also resist the buckling (lube pressure being reduced as lube is stripped in the trip down the bore).
Distortion in either of these manners could easily lead to base perpendicularity issue(s) as the bullet leaves the muzzle, and therefore I think it is meaningful to understand the material properties and section attributes of the projectile in relation to chamber pressure.
For these reasons, I think it is important that bases be thick, lube grooves be shallow & placed as far forward as possible, if chamber pressure is to be increased as far as possible to gain performance.