Q: Strelok Pro Multi BC?

[kezselby]

How do you all go about calculating multiple ballistic coefficient’s to be inputted into strelok? Is a Labradar necessary?



I have been using a single ballistic coefficient for some time and have found that with my 60 yards zero I just cannot get Strelok to correctly true itself so the numbers at every distance I shoot are perfect. If I true it at 70 yards it might be good for 70-100 but a few mils out after that. Or if I true it at 130 it might be correct for 100-150 but after/before that it is a few mils out. I understand that BC changes as velocity changes but is there any way to calculate multiple BC’s for multiple velocities with the use of the BC trueing function in Strelok (from the drop preferably)


All other data is correctly inputted (doubled checked) and using a Weatherflow Weatherstation for weather conditions



Let me know if you have any suggestions!

P.s. this is shooting .30 49.5gn NSA using the G1 Drag Function

 

[ackuric]

Either Labradar or two chronographs set apart at various distances, such as 0-50, 50-100, 100-150, those 3 distances should result in 3 difference bc's. HTH. Not sure G1 is what you want for the 49.5 NSA but IDK about that particular slug...

• G1: Also known as 'Ingalls' (by far the most popular)
• G2: Aberdeen J projectile
• G5: Short 7.5° boat-tail, 6.19 calibers long tangent ogive
• G6: Flatbase, 6 calibers long secant ogive
• G7: Long 7.5° boat-tail, 10 calibers tangent ogive, preferred by some manufacturers for very-low-drag bullets
• G8: Flatbase, 10 calibers long secant ogive
• GL: Blunt lead nose

 

[WAGMASTER]

Kezselby, one more place that can mess you up is in scope settings, particularly what power the scope is calculated at can make quite a difference. 

 

[kezselby]

WAGMASTER, I use FFP so doesn’t make any difference what power I shoot on

 

[Airgun-hobbyist]

It appears that changing the drag function like ackuric suggested will alter the speed at longer distances, which is what truly needs done. The GL setting may work best for airgun initial low speed, and faster drop off from the light projectile, similar to pistol cartridges versus using a G1 setting.

What works for me is tweaking the BC numbers in Strelock based on the point of impact at longer ranges. I haven't tried to see if it effects dialing the short range shots though, so it could very well be doing the same thing you are experiencing. 

 

[JungleShooter]

Kezselby,

there have been a few that published data of variable BC's (really, variable drag....).

Here's one by Bob Sterne (@ GTA) for JSB's domed line in .22cal:

If you're shooting that far out and the Strelok data don't get on on target, there could be a host of reasons, with a wrongly static BC being just one....



Maybe the turret clicks are just a tad off. ➔ Immobilizing the rifle (or the scope mounted to a rail screwed to a table top) will tell you how much your click are off, by clicking the reticle up and measuring if the distance raised at range corresponds to the amount of clicks....

WIth so many clicks needed at extra long ranges, this can make a big difference.



Maybe your ranging is just a tad bit off....

If you open the table with all the ballistic into, check how much just 1 yard ranging error will effect your POI (when shooting at extra long ranges!).

First time I saw this I was shocked.  The POI could easily be half an inch off if I was just 1 yard off in my range estimation....





¿Maybe you got some wind?

Again, for extra long ranges, just see how much wind drift you get for just 2mph of cross wind.

2mph is so light that most humans won't really feel it (and thus, very hard to detect).



Just trying to figure out why the shots don't hit where they are aimed at...!

Hopefully, there is a good solution for you!

Matthias

 

[breed1611]

Guys I’ve read and reread the above statements. When starting where can someone get the basics about making these calculating. Right now it’s very foreign to me. I sure appreciate any guidance.

 

[DonaAna1]

I don't shoot at that distance using an airgun.
But, I went through the same difficulty with powder burners.
You don't need two chronos. You just have to move the one. You just have to move the chrono to true to different yardages. If you are on at 100. Then chrono at 100, get your speed and then chrono at 150. ETC.
And be careful, I shot two chronos.

 

[scoutscope]

Does using multi BC function help the problem?

 

[DonaAna1]

With powder burners, yes.
I don't shoot air far enough to make much of a difference. About 100 yards is it.