Bullet stability
Question:
>You’re right, from an aerodynamic point of view, a spire point at both >ends >is an ideal bullet shape. The problem with this is that there is not as >much >bearing surface and football shaped bullets would be more apt not to >stay aligned in the bore. A secondary problem is that such a shape >lowers >the moment of inertia around the rotational axis so the spin required >for >stabilization would need to be slightly higher.
What type of bullets are we talking here, super-sonic or sub-sonic. From what I understand a boat-tail bullet isn’t more aerodynamic until it goes subsonic, in which case it’s either buried in the target or so far out that it won’t do a lot when it gets there. But I can understand how boat-tail bullets would be better balanced, possibly helping them be more accurate… Also why aren’t the hollow based maxis, for black powder used? Most all the weight is forward and well out from the axis of rotation. just a few more ideas…….Mike To E-mail me remove "no_spam_" from in front of my email address Visit the rec.hunting and rec.hunting.dogs FAQ Home Page at: http://sportsmansweb.com/hunting/ To leave the Hunting listserv list, send a message with SIGNOFF HUNTING
Response:
>The hollow point in benchrest bullets is very small. The improved > aerodynamics from the small hollow point far outweighs the tiny amount > that the hollow point shifts the weight distribution rearward. In > contrast, adding the lead in the back of the Win fail safe bullets > shifts the weight distribution rearward by an estimated 10% of the > bullet length SNIP >The hollow point is small, but the spire shape seriously distorts weight >distribution; the only design that evenly distributes weight is a >wadcutter. If weight forward distribution were an important factor, >then bench rest would have either a five to ten millimetre thick copper >base (to shift the copper core forward), a round nose and a long >tapering boat-tail, or spire points at both ends.
You’re right, from an aerodynamic point of view, a spire point at both ends is an ideal bullet shape. The problem with this is that there is not as much bearing surface and football shaped bullets would be more apt not to stay aligned in the bore. A secondary problem is that such a shape lowers the moment of inertia around the rotational axis so the spin required for stabilization would need to be slightly higher. My point is not that weight distribution needs to be perfectly balanced but that the more a bullet is weighted toward the rear, the harder it is to stabilize. As has been pointed out, rifle bullets are spinning very fast and the contribution of spin and concentricity are usually more important to accuracy than front/back weight distrubution. However, when considering spin rates or concentricity that are on the margin, the bullet with the more forward distribution will fly better. This is clear from arrows, but that is an extreme cases. Shot gun slugs are a middle ground. Some shotgun slugs must be spin stabilized. An exampe is the Remington solid copper saboted slug. The thing will tumble if shot out of a smooth bore. In contrast, the assymetric hour glass shape of Federal saboted slugs is stabilized by a forward weight distribution, and spin is not as critical to its stability. Michael Courtney Visit the rec.hunting and rec.hunting.dogs FAQ Home Page at: http://sportsmansweb.com/hunting/ To leave the Hunting listserv list, send a message with SIGNOFF HUNTING
