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In some .223 forums, I've read flat base projectiles are more accurate within around 200-300 yards, and boattails are better beyond.
Perhaps I've got the limit wrong...perhaps it's more like 100-200 yards.
Anyways, if this is "true", would the same apply to 6.8 with the exception that the lower spin rate (1:10-1:11 barrels) means the accuracy changeover occurs at a shorter distance?
Or, would it be more related to spin-angular momentum, in which case the larger, heavier .277 bullet spinning at a slower rate would end up being about the same.
Interested to hear experienced and expert opinions in this...and thanks for indulging my Sunday night musings.
 

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As far as I know the major difference is a result of the gases at their exit from the bore. The flat base blocks the gases better so it is more stable as flight begins. Flat base 'go to sleep' sooner are less likely to be subject to deformation and less likely to produce flyers so accuracy potential is better for flat base all things being equal. Accuracy over distance has nothing to do with base design per se, but with BC. The effects of BC are exponential over distance. So it is whatever the distance that low BC impacts accuracy/wind performance.

The spin rate question is good one, and others here may know the answer and chime in. My gut tells me the more surface engaged with the rifling and weight are the key. A clue may be the difference between monos and lead cores.
 

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Here is my understanding of the boattail concept, although its not very technical & personally opinionated. Just FWIW....

A bullet, after leaving the barrel, begins to slow down due to drag (friction with the air). At hypersonic speeds the bullet creates an air disruption that radiates around the front of the bullet. As the bullet slows down that air flow begins to collapses around the bullet & because the bullet's butt-end is a boattail, there will be less drag for a longer period, which is the increase in BC.

As to accuracy, I believe the boattail bullet is more accurate just because it is easier for us reloaders to seat it straighter & with less jacket shaving. 😀
 

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There are two types of bullet stability, gyroscopic stability and dynamic (aerodynamic) stability.

Just regarding accuracy and in a nutshell, a boat-tail is more “accurate” at distance because it’s more aerodynamic and therefore has less drop. A flat based bullet flies straighter quicker or “goes to sleep” (an industry term) for a couple of reasons and therefore is more “accurate” at shorter distance.

The “worse” aerodynamic forces acting on the flat base actually work and it’s favor to make it stable in flight. When a bullet leaves the barrel it waggles it’s tail (an industry term). A flat base creates more drag in it’s wake. The higher drag forces pull rearward on the larger surface area of the wider and flatter base. Also, the side forces act perpendicular to the side of the bullet also helping to keep it straight. With the boat-tail, the forces are still present but reduced and just take longer to have an affect.

For a couple of reasons, a bullet is most accurate with just enough spin to keep it stable. Regardless of its forward velocity or aerodynamic shape. Smaller diameter bullets and longer bullets require more RPM for stability. Spin-drift (another industry term) can affect the direction of flight. A spinning cylinder creates lift in the opposite direction to its rotation. A faster spinning bullet creates more lift. Also, any imperfection in the weight density of a spinning bullet can throw it off. Think of an out of balance tire. The faster it spins, the greater the upset.

The above forces apply to bullets traveling supersonic or subsonic. When transonic (going through the sound barrier) different forces are introduced and can have different and destabilizing affects.
 

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Oof, wow, thank you fellas! Here's where I feel like I should ask for a book recommendation....
Not a book, but the article I learned from. I learn a lot from Guns and Ammo. I think I remembered pretty good. Had to look it up to be sure I didn't screw it up to bad.


ETA: Discovered this one looking for the G&A one.

 
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