Range Report My chrono'd loads are telling me something different down range.

[Big Moose]

Been running some Copper Creek 115 DTACs. I've chrono'd these at an average 2910 fps out of my 22 inch barreled gas gun. I run Ballistics AE and if I input the velocity and set the atmospherics etc, it gives me 7.83 mils of elevation to 1000 yds, however this is putting me over the top of the target everytime. When I adjust and dial into the target my actual mil elevation is 7.33, so half a mil high of where I should be, which truing the velocity equates to an avg of 2990 fps. I don't think it can be the scope, which is an ATACR in a Badger mount, which I have run on other guns. Any thoughts or am I missing something here?

 

[Olen_4504]

Twist rate is correct?

Which BC are you using?

Scope height is correct?

 

[Big Moose]

I'm pulling the BC off the table in the program, which is under LItz in the bullet library so I'm assuming that's correct, and the program is up to date. The scope height is correct. the barrel is 7.7 twist, but I don't see anywhere in the program that provides for twist rate input.

 

[ShtrRdy]

What if you used the Litz BC? I assume you're using a G7 BC.

 

[Big Moose]

What if you used the Litz BC? I assume you're using a G7 BC.

Correct I'm using Litz's G7 BC, which is in the program.

 

[canezach]

Ballistic AE might be giving you the old BC for the original DTACs. I believe the BC numbers for the newer DTACs are 0.305 G7, so if you're seeing a G7 BC of 0.276, that's for the original DTACs, not the new ones

 

[Big Moose]

Ballistic AE might be giving you the old BC for DTACs. I believe the new BC numbers were 0.305 G7, so if you're seeing a G7 BC of 0.276, that's for the original DTACs, not the new ones

Wow thank you, that makes a whole lot of sense, just ran the numbers with the new BC and that there is about the difference.

 

[ShtrRdy]

I'm glad canezach was able to give you exact numbers to consider. This is basically what I was asking.

 

[Big Moose]

I'm glad canezach was able to give you exact numbers to consider. This is basically what I was asking.

Thanks, that explains the half mil difference at just over 1000 yds.

 

[wvlapua]

I'm having the same problem today. Labradar tells me 2917fps. When I do velocity calibration it changes to 2992fps. I'm using .620 g1 bc for the 115 DTAC RBT.

Actual dope
500 yds = 2.3 mils.
990 yds = 7.0 mils.

Shooter app
500 = 2.5
990 = 7.5

 

[canezach]

I'm having the same problem today. Labradar tells me 2917fps. When I do velocity calibration it changes to 2992fps. I'm using .620 g1 bc for the 115 DTAC RBT.

Actual dope vs Shooter app
500 yds = 2.3 mils. Vs 2.5
990 yds = 7.0 mils. Vs 7.5

I'm not familiar with Shooter, but the first thing I'd check is the data you enter yourself: atmospherics, scope height, etc..

 

[Big Moose]

I'm having the same problem today. Labradar tells me 2917fps. When I do velocity calibration it changes to 2992fps. I'm using .620 g1 bc for the 115 DTAC RBT.

Actual dope
500 yds = 2.3 mils.
990 yds = 7.0 mils.

Shooter app
500 = 2.5
990 = 7.5

See post 5 above, I was using the old G7 BC .276 instead of the new G7 BC for the new DTAC, which is .305. looks like you did the same. I'm using Ballistics AE and the bullet library obviously isn't up to date.

 

[wvlapua]

I'm not familiar with Shooter, but the first thing I'd check is the data you enter yourself: atmospherics, scope height, etc..

Will do

 

[wvlapua]

See post 5 above, I was using the old G7 BC .276 instead of the new G7 BC for the new DTAC, which is .305. looks like you did the same. I'm using Ballistics AE and the bullet library obviously isn't up to date.

0.620 is the G1 for the RBT. Ill try the G7

 

[b6graham]

0.620 is the G1 for the RBT. Ill try the G7

That BC is only for the exact barrel and load it was calculated from. You barrel and bullets may be slightly higher or lower depending on a lot of factors

 

[wvlapua]

That BC is only for the exact barrel and load it was calculated from. You barrel and bullets may be slightly higher or lower depending on a lot of factors

If I don't run my pressure as absolute, instead use altitude, the program is much closer. I'm gonna take the kestrel next time out and sink it up with my ballistic app to remediate any issues on that front, then work from there.

I played with bc a bit but I had to take it up to .700 to make up the difference. No way it's that high.

 

[b6graham]

If I don't run my pressure as absolute, instead use altitude, the program is much closer. I'm gonna take the kestrel next time out and sink it up with my ballistic app to remediate any issues on that front, then work from there.

I played with bc a bit but I had to take it up to .700 to make up the difference. No way it's that high.

Atmospherics/DA way off?

 

[wvlapua]

Atmospherics/DA way off?

No, I entered the exact same elevation, temp and humidity. By using elevation instead of station pressure I was within 0.2 mil. I recently went into the settings and changed them to run DA next time out.

 

[7magsavage]

Make sure your target angle (look angle) is correct. I have screwed with mine before and forgotten to change it.
Had similar issues. Makes a decent difference at a grand.