Written by Sierra Bullets Chief Ballistician Tommy Todd
A question we often have to answer here at Sierra is referencing bullet shape and how accurate it is. An example would be the Sierra #2130-30 caliber 150 grain Spitzer bullet and the Sierra #2125-30 caliber 150 grain Spitzer boat tail bullet.
“So which one is more accurate?” is the usual question.
If we did our job correctly in the manufacturing of the two bullets they have equal accuracy potential. The only real difference between them is the shape of the base of the bullet (flat-base as compared to boat tail). This shape difference does not change the potential of accuracy, but it DOES change how the bullets shoot in individual guns and possibly the load required to deliver optimum accuracy. Sometimes a shooter will do a load workup and hit an accuracy node quickly with one bullet and have good accuracy, but when they switch to a similar bullet they experience a lesser accuracy with a similar load workup session and decide the first bullet “shoots better” in that gun. If both bullets are produced to equal accuracy potential, it is most likely that the load workup missed the combination that would optimize the accuracy of the second bullet and more testing would reveal that accuracy potential. Before I get in hot water with a lot of you shooters, this is not always the case and sometimes guns just WILL NOT shoot the second bullet design despite any load utilized.
I have also had shooters inquire if a bullet with a higher ballistic coefficient (BC) (more efficient shape) is more accurate than one with a lesser BC. This scenario is very similar to the one written above. Despite the bullets being shaped differently if produced the same the accuracy potential is equal even if the efficiency (BC) of the two bullets are different. The shape of the bullets can and does change the load tune (combination of powder charge, distance from ogive to barrel rifling, neck tension etc) and how finicky that a bullet is to changes or variations of the load that makes them shoot to their potential. Again, before I get in trouble with you shooters, please realize that I am referring to sheer accuracy in a NO WIND condition, it goes without saying that the higher BC bullet is usually more desirable in the environmental conditions we have to shoot in.