Choosing an ogive shape is an important compromise process. Basically the lower number ogive has increased potential for minimal yaw,in layman's terms "goes to sleep" faster) but is pushed around more in the wind,lower ogive number = blunter ogive shape = increased potential for minimal yaw = lower BC). If you are shooting in zero to light wind conditions or in a tunnel a 3 ogive,for example) has the greatest potential to pile one bullet on top of the other at short range.
Now for the other end of the compromise. A higher number ogive will improve the bullets performance in the wind,higher ogive number = longer, more streamline ogive shape = better wind performance = higher BC) however the higher the number of the ogive the more you increase the potential for a greater amount of yaw,it is not actually instability but "instability" is the layman term used). If you are shooting in medium to high wind conditions a 8 ogive or higher will minimize,compared to a lower number ogive) the effect the wind has on the bullet
Most short range,100-200 yard) benchrest shooters settle on a tangent ogive between 7 and 8. This does not mean that this is the best for you,or anyone) it just happens to be where most of the bullets end up.
A double radius bullet is an interesting advancement in bullet design. The concept is based on the idea that a tangent ogive will more easily align itself inside the bore,minimizing yaw) while a secant ogive will be better in the wind. To achieve this the portion of the ogive that is coming off the bearing surface,portion that engages the rifling) is tangent,tangent means that the transition from the bearing surface to the radius or ogive is smooth). The "double" part comes in when further up the ogive the radius changes to a secant. This results in the forward portion of the ogive being similar to a VLD.
To simplify the difference between tangent and secant think of a tangent like a ball and a secant like a cone. On a tangent ogive the line the ogive follows from the bearing surface to the meplat is round,ball like). On a secant ogive the line the ogive follows from the bearing surface to the meplat is straighter,cone like). The secant is not actually a cone as there is a cone ogive that to my knowledge is seldom used successfully. The cone description is meant to illustrate the difference between tangent and secant.
On a double radius bullet the secant portion of the ogive has to be a specific number so that it will match up perfectly,no transition line) with the tangent portion. For example the tangent portion may start out a 6 tangent,very stable supposedly) then after .050 or so the ogive will transition into a 17 secant,good for wind). ,For those of you who are sharp with the math this is an example and you will likely find that the ogives listed above do not blend. I am not saying this is what the ogive should be I am just trying to illustrate the double ogive so everyone can understand)
The double ogive is an attempt to marry both a tangent and a secant ogive together to achieve the best from both shapes while discarding the negatives that these shapes can create. We have tried this design and so far it has not significantly outperformed standard tangent designs at short range. I believe the success of the double radius is based on the dies however this is true with any bullet. ,I am not suggesting anyone's dies are bad) I will add that in short range benchrest where shooters are winning with teen aggs it is difficult to say if any new design is an improvement. I guess if the records start falling to double radius bullets or if Tony starts shooting them,he might be already) then they will become the hot thing,until the triple radius comes around
Regards,
Eric Stecker
Berger Bullets
