Quote:
Originally Posted by Eddietruett
.... And I can't figure out why one bullet has so much variance compared to the other 2. When I got home, I did check the diameters of all and they are all dead on .357" and checked about 25-30 random Speer bullets expecting to see a slight difference in diameter but everyone I checked was dead on the money. Am I just over thinking this?
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You're nibbling around the edges of the issue here .... it's consistent pressure that translates to consistent velocity. Pressure consistency is correlated to bullet pull, which is affected by case wall thickness, crimp and, yes, bullet diameter, both absolute and relative (to chamber diameter).
What does "dead on .357" mean?
If one uses calipers and not a micrometer, they really have do idea.
Significant bullet diameter differences are measured in ten thousandths of an inch. A caliper can read ".357 dead on" with a bullet that is .3565 and another that is .3574 ... practically .001" different in reality.
Stack tolerances on brass thickness, crimp variance due to slight variation in case length, and true bullet diameter and ES of 100fps is very believable. As to the real world significance of such ES with respect to accuracy (precision) ... the paper doesn't lie.
IMO, statistical evaluation of handgun accuracy is navel-gazing. I can shoot 2, 10-shot groups with each different load from a Ransom rest and make a $100 bet on which will be the most accurate in that gun forevermore.