June 01, 2011
Check with any Highpower shooter worth a shot, and he or she will most likely tell you to use boattail bullets for the best accuracy. The 1,000 Benchrest crowd will probably tell you the same. But ask the "short-range" Benchrest shooters — -the ones who literally compare the size of one-hole groups to see who wins — -and you're more likely to be sent after a box of custom-made flat-base bullets. Why the difference? Both long- and short-range shooters are looking for the smallest groups, the best ballistics, the greatest accuracy, and the highest possible scores. What works for one should work for the other, right? Not necessarily.
There's less that can go wrong in manufacturing a flat-base bullet, with the main points being that the bullet is round and the base is square to the bearing surface, or bourrelet. Because they can be manufactured to higher tolerances and less manufacturing variables, flat-base bullets are inherently more accurate than boattail bullets.
Compared to flat-base bullets, it's more difficult to manufacture accurate boattail bullets. Bullets are formed in dies, and the boattail alignment will always be off by 1/2 the amount of clearance between the punch and the die. Tolerances have to be extremely tight. In a manufacturing environment, it's simply not possible to put boattails on perfectly square or perfectly straight.
Boattails increase the ballistic coefficient of bullets, which helps them overcome air resistance and wind deflection. The shape also helps the air flow transition over the heel of the bullet and reduces the base diameter resulting in less base drag. Understand that at supersonic velocity, nose drag is the primary drag component, so the base drag benefit of a boattail really doesn't come into play until the bullet is transitioning to or at subsonic velocity.
The difference in the amount of drop between flat-base and boattail bullets won't amount to much until well past the range at which most of us shoot, but the boattail's better ballistic coefficient makes errors in wind deflection correction and range estimation more forgiving--especially for lower velocity loads. Whatever loss of accuracy there is from the boattail's inherent manufacturing flaws are more than offset by their ability to overcome adverse or unknown shooting conditions.
So what should you shoot, flat-base or boattail bullets? Personally, I think that regardless of whether you're shooting game or punching paper, you should try several brands of boattail and flat-base bullets and then shoot whichever one is most accurate in your gun at the range and in the conditions you intend to shoot. Whichever you choose, most Benchrest shooters who shoot at relatively close range will stick with the flat-base bullets until someone starts winning with a particular type of boattail, and the Highpower shooters and 1,000 yard Benchrest shooters will probably stick with boattails for their long-range benefits.