"...difference in bullet shape versus seating stem..." That's on the point only. The point makes no difference for accuracy. Only the base of the bullet matters. Bashing the 8 rounds with an SP in a Garand clip on the butt plate deforms the point, but does nothing to alter the accuracy.
However, bottle necked rifle cases need to be chamfered and deburred on the case mouth. That takes the place of the flare done to a handgun case for seating.
"...dent in the ogive..." Has nothing whatever to do with the BC. Ballistics Coefficient is a measure of its ability to overcome air resistance in flight. There's a physics formula. BC = Sectional density/ Coefficient of form. The latter is derived by 6 methods and applied differently depending on the trajectory models used.
Ok really not poking fun or trying to start an argument, and I’ve appreciated some good posts from you, but... The first and second statements here are both factually incorrect and generalizations; while the effects of both are small compared to other controllable variables what you said just is not true.
1) an off-center bullet tip while spinning at speed will increase the bullet’s susceptibility to drag by creating turbulent flow rather than laminar flow near the ogive with shallower boundary layers and increasing susceptibility to wind drift. In that respect it affects accuracy even if fired on a perfectly calm day with no change in atmosphere between you and the target due to turbulence and your calculated to actual trajectory will have greater variation than if the bullet tip was perfect. One bullet flight and the next will vary, accuracy is a measure of ability to predict flight correctly each time. Consistency is a measure of ability to repeatedly be accurate. Does it matter? Maybe, probably not, depends how well larger variables are managed. But to say it has “no difference” is factually incorrect. Bashing in tips may have resulted in accuracy change too small for you to measure but it is impossible for it to not change (I’ll admit that is an interesting observation from a test if just that).
2) the ogive being different from an indentation compared to the reference bullet shape most certainly does change the true/effective bullet efficiency while your calculated/approximated value based on a reference shape (B.C) will now be more wrong than it was. B.C. itself is a derived parameter which we (for simplicity) use an approximation by one of the reference shapes for which an empirically known value exists but your bullet will never be exactly that so we have a relative approximation from known reference to our bullet; when your bullet is no longer what it was your relative approximation cannot still be the same. The reference coefficients are dependent on the rate at which the diameter expands (ogive) as well as the base shape and length which is why a reference exists for G1 and G6 which have only a difference in length and ogive radius. You can create a G6 variant just by changing the radius and calculate that if you want to, there are an infinite number of reference models; ballistics calculators may have 9 or more of them. The ogive change by the indentation and bullet tip concentricity may result in increased susceptibility to drag if there is no longer body of revolution (perfect symmetry) on which to base the empirical calculation. Turbulence may not occur but maybe just changed depth of boundary layer for a subtle/smooth indent. Again, maybe doesn’t get into the noticeable but also not “nothing whatsoever to do”.
Avoid anything irregular if possible. Bent bullet tips are avoidable as are mangled bases.
Andrew - Lancaster, CA
NRA Life Member, CRPA member, Calguns.net contributor, CGF / SAF / FPC / CCRKBA / GOA / NAGR / NRA-ILA contributor, USCCA member - Support your defenders!
