bullockcm said:
EShell, can you elaborate a little more, not sure I understand. By base of the bullet do you mean opposite the HP in this case? You mention putting the opening in front allows the base to be perfectly formed, I guess I don't understand why the base can't be perfectly formed regardless of what is done at the front of the bullet?
During production, the bullet must be closed around the core "somewhere", either the front or the back. There are always tolerances and inconsistencies in any process. By putting the closure point in front, we end up putting the result of these inconsistencies up there too.
For example, we have a variable length and thickness jacket cup that will finish at varying lengths and provide varying resistances to the forming die mechanism. Intense QC keeps these variations very small, but, they continue to exists and the pursuit of accuracy is the pursuit of perfection, and nothing is perfect
The lead core weight/length/diameter can also vary slightly, which produces variations in the place the finished core ends up inside the jacket, and also providing varying resistance to the forming die. Varying resistance = varying shape.
By referencing everything to a closed bullet base and working forward, we force all of these inconsistencies forward, to the less important tip.
The minor jacket length variations translate to differing meplat length and shapes. Jacket thickness variations change the ogive slightly. Neither of these items are particularly important to short range accuracy, not when compared to the base. The newest fad of trimming meplats in long range bullets then addresses this front end inconsistency, and sorting match bullets by bearing length minimizes the effects of ogive position.
Core length and diameter variations result in a difference in where the front of the inserted core end up. The hollow point design leaves a gap between the end of the core and the front of the jacket, so the effect of this minor core variation is lessened.
If we began forward and worked back toward the base, all of these variations will show at the end where we would finish. Core length differences will influence the way the jacket is rolled over the end of the bullet. Jacket length differences will change how much jacket ends up rolled around, as will jacket thickness differences. All of these minor (taken alone) variations will work to make the bases inconsistent, and again, the base is much more critical to the bullet's accuracy potential than the nose.
As a result, FMJ bullets are notoriously less accurate than soft point or hollow points. The only FMJ match bullet I'm aware of is Norma's 6.5/130, and "nobody" actually shoots these things in competition.
Close range (100/200/300 yard) benchrest competition, the most demanding on the equipment's absolute accuracy levels, use a flat base HP bullet exclusively. This is because the flat base is easier to form consistently than the boattail and provides a relatively longer bearing surface to weight ratio.
Long range (600/1,000 yard) benchrest competition, only slightly less demanding on absolute equipment accuracy, but more demanding of bullet performance and uniformity, uses boattail HP bullets exclusively. This is because the boattail, while slightly less precise, works better to negate the more severe effects of environmental factors. The more aerodynamic boattail has less drag and both drops less and is pushed by the wind less. Less overall drop & drift also means that minor variations in velocity and wind speed/direction changes also have less effect.
With the current 100 yard BR record at less than .1" and groups less than .2 are quite common, and the 1k BR record at around 1-1/4" with groups less than 4" quite common, accuracy standards are indeed high. Competition is fierce, and if FMJs showed any promise, or rather, if FMJs were not so markedly and consistently inferior, these would be the bullet of choice, but, they're not.
