super to trans to sub
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std7mag
Well-Known Member
I'd wager any bullet with sufficient weight and BC.
I remember either an article or interview with Bryan Litz about going from super sonic to subsonic.
Something about rifling twist rate being on the slow side for bullet weight actually did better going from supersonic to subsonic.
I remember either an article or interview with Bryan Litz about going from super sonic to subsonic.
Something about rifling twist rate being on the slow side for bullet weight actually did better going from supersonic to subsonic.
MagnumManiac
Well-Known Member
I am unsure if this is correct, but boattail bullets are worse for transition from supersonic to subsonic. I remember reading a shorter flat base bullet transitioned smoother, but my memory isn't good at all anymore.
Someone can correct me if I have it backwards.
Cheers.
Someone can correct me if I have it backwards.
Cheers.
dfanonymous
Well-Known Member
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Transonic performance is hard to predict. A lot of it has to do with bullet design. I see that's getting touched on as I'm typing. Specifically, the common denominator I've seen between **** bullets and good ones at subsonic have to do with where COG was, relative to said bullet.
As far as stability, you want a good stability factor.
A bullet that leave unstable will remain unstable, and when transonic shock waves hit, it'll fly all wonky and backwards.
The caution with longer bullets is that they are more prone to pitching and yaw. However, I have and others have been able to get repeatable results at ranges exceeding 50% distance of transonic via subsonic with long bullets. Like I said, it can be tricky. With dragging out subsonic that far, a matter of atmospheric change can cause dramatic shift in results at times.
As far as stability, you want a good stability factor.
A bullet that leave unstable will remain unstable, and when transonic shock waves hit, it'll fly all wonky and backwards.
The caution with longer bullets is that they are more prone to pitching and yaw. However, I have and others have been able to get repeatable results at ranges exceeding 50% distance of transonic via subsonic with long bullets. Like I said, it can be tricky. With dragging out subsonic that far, a matter of atmospheric change can cause dramatic shift in results at times.
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CheyTac recently patented a bullet design that remains stable through all regimes. They have an extensive article on spin, stability and drag written by John Taylor here:
Balanced Flight Projectile
You will need a custom rifling profile to make it work.
Balanced Flight Projectile
You will need a custom rifling profile to make it work.
MagnumManiac
Well-Known Member
BC is a definitive factor. When we developed our CNC turned brass solid in .338" at 323g it was determined that the shape we were trying for and the resultant weight was going to have to be a compromise on length. The BC needed was G7 .399, we fell short of this due to length and had to compromise.
Cheers.
Cheers.
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Mikecr
Well-Known Member
I see accuracy as the most powerful ballistic attribute.
Given this, I limit my range to supersonic and no lower.
At the transition -transonic & below, there is a bullet's dynamic stability in play (different than gyroscopic stability).
This is not predictable and can only be tested to see what happens throughout a range of conditions.
Not worth it for my needs
Given this, I limit my range to supersonic and no lower.
At the transition -transonic & below, there is a bullet's dynamic stability in play (different than gyroscopic stability).
This is not predictable and can only be tested to see what happens throughout a range of conditions.
Not worth it for my needs
Super and sub velocities seem to be the more predictable outcome as the transition to trans isn't abrupt but does seem to be an issue? I try to stay in the super range also. This thread is a food for thought to pick my brain and others that are curious and might have answers. Your input is welcome.
Mikecr
Well-Known Member
I couldn't run a drop chart through transonic, because I couldn't guess what drag will do there.
The same dynamic stability changes could affect bullet path beyond.
The same dynamic stability changes could affect bullet path beyond.
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This is all why the long range 22 rim fire guys try to have muzzle velocity at the top of the subsonic range
Black Hat
Well-Known Member
The .30 Berger Juggernaut OTM Tactical
was designed by Bryan Litz to remain stable through the transonic to subsonic stage for extended range out of the .308 Win, this was to prevent the keyhole at the target.
I've tested them at 1200 yards and found no loss of accuracy or stability, however they would have been just hitting that transonic stage at that distance.
was designed by Bryan Litz to remain stable through the transonic to subsonic stage for extended range out of the .308 Win, this was to prevent the keyhole at the target.
I've tested them at 1200 yards and found no loss of accuracy or stability, however they would have been just hitting that transonic stage at that distance.
Please read the article I linked above and you will see that this issue has been solved by CheyTac and they have a patent on it.
Their .408 419 gr bullet hit a target at 3800 yards. That is over 2 miles. It goes subsonic at about 2500 yards. The G1 BC of .949 remains constant over that entire range. Please note that you must have custom rifling to use this bullet.
Here is the link again:
Balanced Flight Projectile
