Range Report Consensus on transonic velocity

[TimeWillTell]

So I've seen a lot of things stated that people use, 1200 fps, mach 1.1, 1.2, 1.3... What is everyone using? Is there a true consensus vs internet "know it all"? As I reach out further I'm just trying to wrap my head around the numbers some and when I'm reaching that point where bullets flight starts to be effected by transonic flight.

 

[_Windrider_]

If you look at CB or FFS as well a few others, most I know are using 1.2 thru .8.

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Agreed, although the exact transition from supersonic to subsonic depends on temperature. the colder it is, the longer the bullet stays supersonic.

 

[TimeWillTell]

Thanks Diver that helps a lot. For me right now ELR is 1350 in my geographical area so just trying to understand transonic as I am flirting with it or moving into it with my 6.5 Creedmoor.

 

[_Windrider_]

I think you got that backwards

well, i guess it depends how you read it. to clarify, the colder it is, the lower the speed of sound is. so depending on starting velocities and temps and such you could reach subsonic at a shorter range, but the velocity at which the speed of sound occurs will be lower. does that make more sense?

it might be 1200 at 80F but 1046 at 42F (totally made that up to illustrate...not real numbers).

 

[Tjfarmer]

does the newer 5700elite kestrel with the AB work well for bullets running slower then 1100-1200. On the fence as far as getting my first one, hoping it’ll dial that in better.

 

[_Windrider_]

does the newer 5700elite kestrel with the AB work well for bullets running slower then 1100-1200. On the fence as far as getting my first one, hoping it’ll dial that in better.

AB works in subsonic best with CDM's and using DSF. But it isnt perfect.

 

[TimeWillTell]

Thanks you diver. I'd love to get into ELR down the road when I have more money and time to get a place to shoot but for now it appears that with my max range of 1350 with 6.5 Creedmoor running around 2850, I don't have a ton to worry about. So, good for my shooting, not so educational for my quest to understand exterior ballistics better. Maybe I'm play with 223 more in the near future to explore further.

 

[_Windrider_]

Well not really in anyway meaningful.

Think the 3 “H”s when selecting a lower drag area.

High, Hot, Humid - the more of those especially together the longer the bullet will stay suppersonic .

Ignoring density, if the only change was temperature from say 50 to 40, you would reach subsonic speeds (I’m talking true Mach 1.0, not the transonic region of 1.2 to 0.8) at a further range because the speed of sound is slower in colder temps.

Putting density in, it is likely you could not get the same distance due to the rate of speed decay due to air density changes.

 

[_Windrider_]

I hope you see this as a conversation and not me trying to be argumentative. In no way is my intent.

It seems no matter what happens the increased drag caused by the colder temperature outpaces and slows the projectile and thus the distance more than the sound barrier’s decreases speed. The reason I put some examples down into different station pressures, was to show that they both responded to temperature the same way. If you look on the same line, you’ll see that every time it gets cold in each of the station pressures the supersonic distances get pulled back.

But the real weird deal is strong wind and super cold like freezing temps also seem to depart from what might be expected.

Anyway is all so close and other conditions seem to effect the real outcome a lot.

That’s why that written dope still seems to over-ride all this stuff anyway.

No man. Two guys chatting. We agree that the colder the air subsonic speed will be reached at a closer range.....could be just a few feet. My whole point was though that the speed is slower in colder air. That’s all. Between 50 and 40 I thinks it’s something in the realm of 6fps. When I said longer I meant in terms of speed not distance.