Hornady 30 cal 250 A-tip bc value

[Schw15]

What is everyone else seeing with the bc on these bullets?

 

[Pete Cefalu]

What is everyone else seeing with the bc on these bullets?

Using the published BC gets me occasional 1st shot impacts at 1300
However, I only get in the ballpark at a mile with several attempts, and in the zip code at 2000.
So I started testing with the Kestrel MV truing and Drop Scale Factor(truing the BC) with a friends 308 Winny as a dry run.
It worked flawlessly. He had 1 shot impacts up and down the range from 400-1000.
As for our 250's in the 300WM, I am going to try an true the MV at the mile as it is 90% of before going trans, and then the 2000 to true the BC after it hits subsonic(1955@2750MV on calculator). All of this is dependent on the SG being very stable of course.

 

[Schw15]

I had to play with my numbers I ended up moving g7 to .475 from .442 and was hitting at 1 mile and 1800 yards.

I was just curious what others were seeing and people had same issues like that

 

[Pete Cefalu]

I had to play with my numbers I ended up moving g7 to .475 from .442 and was hitting at 1 mile and 1800 yards.

I was just curious what others were seeing and people had same issues like that

Well you are up in higher thinner air, I'm down here in a sauna. Do you own a Kestrel?

 

[Schw15]

Well you are up in higher thinner air, I'm down here in a sauna. Do you own a Kestrel?

I use strelok pro app and I have a Kestrel just for wind temp and elevation ect.

Yes 1-8 twist and 5400 elevation

 

[6.5SH]

Hornady's banded BC's are:

30 Cal 250 gr A-Tip® Match Bullet
0.878 G1
0.442 G7
0.877 G1
0.440 G7
0.872 G1
0.439 G7

The PDM's in AB Mobile for G7 vary from:
464
459
452
447
441
440
435
431

ETA:
Hornady's listed single BC is .442 G7, where did .475 come from?

 

[Pete Cefalu]

I use strelok pro app and I have a Kestrel just for wind temp and elevation ect.

Yes 1-8 twist and 5400 elevation

Gotcha. So out of curiosity, if you left the published BC in the calculator, and slowed down the MV instead, would that give you the same firing solution as the increased BC?

 

[Schw15]

Gotcha. So out of curiosity, if you left the published BC in the calculator, and slowed down the MV instead, would that give you the same firing solution as the increased BC?

I have to increase velocity by 53 feet to get same data. I use a magnetospeed v3 off the barrel mount.

Seems like from up above the bc are all over the place

 

[Schw15]

Hornady's banded BC's are:

30 Cal 250 gr A-Tip® Match Bullet
0.878 G1
0.442 G7
0.877 G1
0.440 G7
0.872 G1
0.439 G7

The PDM's in AB Mobile for G7 vary from:
464
459
452
447
441
440
435
431

ETA:
Hornady's listed single BC is .442 G7, where did .475 come from?

I had to change the bc to .475 to match my drops out to 1 mile.

 

[6.5SH]

I have to increase velocity by 53 feet to get same data. I use a magnetospeed v3 off the barrel mount.

Seems like from up above the bc are all over the place

On the PDM's it doesn't tell you the velocity that gave that result, so can't really take those as averages. A 53 fps adjustment to true is way less severe than .035 BC increase unless his velocity is from some barrel burner.

 

[6.5SH]

I had to change the bc to .475 to match my drops out to 1 mile.

That seems way high for truing, does it alter the rest of your dope closer in? Or is this some super high velocity cartridge?

 

[Schw15]

That seems way high for truing, does it alter the rest of your dope closer in? Or is this some super high velocity cartridge?

Pushing them 2783 now had them 2880 but went with a lower node. I was just testing loads at distance I've shot them from 866 to 1450 1760 and 1800. Different days but all shot high with data.

 

[6.5SH]

Pushing them 2783 now had them 2880 but went with a lower node. I was just testing loads at distance I've shot them from 866 to 1450 1760 and 1800. Different days but all shot high with data.

If they were all high then I'd say one of your inputs is wrong. Likely the zero distance or you had some offset that wasn't accounted for.

A good read on all the little things that can add up:

Ballistic Program Inaccuracies

 

[Schw15]

I finally got a load so hopefully I can test it soon from 800 to 1000 and keep moving back to see how it lines up. I just thought that was a lot of truing on bc I know sometimes the bc can be more. That's why I was interested in what everyone else is using for bc. Awesome I will look

 

[Pete Cefalu]

Sorry to disappear mid flight, my time zone got me. Not to keep harping on Kestrel(5700 Elite with AB installed), but it will provide you the exact yardage to true the MV first, and then the exact distance to true the BC. With these two tasks complete, a change in MV will no longer have an effect on BC. At least that’s my understanding. Please know(as I think you do), that I am in no way an expert on aerodynamic flight, just mentally(and financially) invested.