- Thread starter otnot
- Start date
1000's of yards.....Mark and Sam after work shoot pretty accurately to 3000 and 4000 yards and beyond, long past where the bullet is subsonic.
It depends. Some bullets handle the transsonic region gracefully and some bullet will upset and become unpredictable. Even the rifling itself and bullet engraving can affect this transition.
So do longer bullets transition better? How about heavier bullets? I've noticed that the solid copper bullets are long and very pointed. I was also wondering if a bullet is like a top? The faster the spin the more stable it is and as it slows down it begins to wobble. I take it if that is true for bullets, then a fast twist barrel and solids would be the way to go.
Transonic Ballistics Effects Explained by Bryan Litz
What happens when the bullet slows to transonic speed, i.e. when the bullet slows to about 1340 feet per second? It is getting close to the speed of sound, close to the sound barrier. That is a bad place to fly for anything. In particular, for bullets that are spin-stabilized, what the sound barrier does to a bullet (as it flies near Mach 1) is that it has a de-stabilizing effect. The center of pressure moves forward, and the over-turning moment on the bullet gets greater. You must then ask: “Is your bullet going to have enough gyroscopic stability to overcome the increasing dynamic instability that’s experienced at transonic speed?”
Some bullets do this better than others. Typically bullets that are shorter and have shallow boat-tail angles will track better through the transonic range. On the contrary, bullets that are longer… can experience a greater range of pitching and yawing in the transonic range that will depress their ballistic coefficients at that speed to greater or lesser extents depending on the exact conditions of the day. That makes it very hard to predict your trajectory for bullets like that through that speed range.
When you look at transonic effects on stability, you’re looking at reasons to maybe have a super-fast twist rate to stabilize your bullets, because you’re actually getting better performance — you’re getting less drag and more BC from your bullets if they are spinning with a more rigid axis through the transonic flight range because they’ll be experiencing less pitching and yawing in their flight.
-------
IIRC the rotational velocity of a bullet doesn't decrease a ton on the way to target since the drag in that direction is so low, that being said a faster twist rate doesn't hurt until you start blowing up bullets.
What happens when the bullet slows to transonic speed, i.e. when the bullet slows to about 1340 feet per second? It is getting close to the speed of sound, close to the sound barrier. That is a bad place to fly for anything. In particular, for bullets that are spin-stabilized, what the sound barrier does to a bullet (as it flies near Mach 1) is that it has a de-stabilizing effect. The center of pressure moves forward, and the over-turning moment on the bullet gets greater. You must then ask: “Is your bullet going to have enough gyroscopic stability to overcome the increasing dynamic instability that’s experienced at transonic speed?”
Some bullets do this better than others. Typically bullets that are shorter and have shallow boat-tail angles will track better through the transonic range. On the contrary, bullets that are longer… can experience a greater range of pitching and yawing in the transonic range that will depress their ballistic coefficients at that speed to greater or lesser extents depending on the exact conditions of the day. That makes it very hard to predict your trajectory for bullets like that through that speed range.
When you look at transonic effects on stability, you’re looking at reasons to maybe have a super-fast twist rate to stabilize your bullets, because you’re actually getting better performance — you’re getting less drag and more BC from your bullets if they are spinning with a more rigid axis through the transonic flight range because they’ll be experiencing less pitching and yawing in their flight.
-------
IIRC the rotational velocity of a bullet doesn't decrease a ton on the way to target since the drag in that direction is so low, that being said a faster twist rate doesn't hurt until you start blowing up bullets.
for 168 smk’s? yes this is actually an accurate graph
they might have fixed them since, but I read in alot of places that there is a design flaw in the boat tail in that specific bullet on the that causes them to go haywire when transitioning to sub.My 168 SMK's have never seen that graph apparently
even so much that some ranges banned them for 1000 yard competitions due to safety of the people working in the pits.
Thanks
The 169 SMK shoots better at a 1000 than the 175 SMKMy 168 SMK's have never seen that graph apparently
Longer bullets dont alway transition well its more about design and being properly stabalized. Weight has nothing to do with transitioning again its all about design. Solids are longer cause there is no lead to make them heavy. So extra mass is needed for weight . Extra sharp pointed bullets can have better bc's some times but that in it self can cause stability issues sometimes. Gyroscopic stibility is realized in a top but a bullet is not attached to a table so there are lots is dis simular attributes. And you need to take into consideration that time of flight is a very short time frame even at extreme distance. so a bullet never has a chance really slow down in its spin rate. But a little extra stabalized spin rate does some what help but it wont make a poorly designed bullet great. Again its all about bullet design . There are other things that can help like bullet run out. Throat design (how straight a bullet engages the lands )
I wouldn't call the 13 degree boat tail a design flaw. The bullet was designed for 300 m competition and did very well for that purpose. The issues arose when guys where shooting them at distances they weren't designed for.
Transonic 2/3 of the way to the target? I mean, at some point the transonic zone transitions to subsonic, right?
Oh definitely. The bullet doesn't spend a bunch of time in trans, looking at my calculator my bullet goes into trans at 2150 ish yards and is subsonic by 2350 ish
I just finished building my 338 Lapua IMP based on a KS Arms LAR3 action and 32" 1:8 blake barrel.
My goal is to score a hit at 2 miles (3200m).
Plan on shooting 285 warner Tool Flatlines and my load runs 950m/s. it hits sub sonic at 2400m give or take some.
Anyone experience with the flat line 285s regarding transsonic? My total elevation to work with is 52mil in this rifle calc says 49mil will be needed at the 2 miles.
My goal is to score a hit at 2 miles (3200m).
Plan on shooting 285 warner Tool Flatlines and my load runs 950m/s. it hits sub sonic at 2400m give or take some.
Anyone experience with the flat line 285s regarding transsonic? My total elevation to work with is 52mil in this rifle calc says 49mil will be needed at the 2 miles.
Time is relative depending on how well it transitions even if it's a split second and it's a shitty bullet your opposed hosed
