Ballistic ? actually a couple

[Caveman0101]

1. I'm shooting at 7500' elev. Temp 68F, H41%, Pr 29.9 inHG. When I put that into the calculator (I've tried several) and I change the elevation and temp for expected hunting condition, the calc changes the pressure to something like 22.8 inHG. WTH, I check the pressure in Leadville (about 50 miles away at 10200') and it always within a few tenths of where I'm shooting, actually last time we shot it was a tenth higher than shooting location. What gives? Should I not worry about this or should I change the pressure to match what weather stations nearby at higher elevation are reporting?
2. I'm having trouble with the calc matching what I'm seeing on target. I'm shooting 142gr ABLRs using updated G7 BC. I'm shooting 3.5" high at 100 and 2" low at 300. The calc is saying my vel. is 2900+, my chrony is saying 2650, I know 2900+ is not right, but I'm not sure how to reconcile this with the calc. I will be doing actual shooting to confirm all drops out to 800 and there have always been small differences between calc and target in the past but not this much. Any suggestions? (having the same problem with .284 also)

 

[pbatesaz]

Sounds like it is coming back with a station pressure instead of the corrected barometric pressure that you are entering. Perhaps try entering station pressure. Station pressure in Leadville this morning is 21.005 in Hg.

 

[FN-Whitney]

Download the free Hornady app, its very easy to use. True your bc to your actual dope, make sure all the environmental data is correct not close but the best most accurate you can get. Then test the dope on different days with varying conditions to see if it is giving you correct adjustments.

 

[_Windrider_]

1. I'm shooting at 7500' elev. Temp 68F, H41%, Pr 29.9 inHG. When I put that into the calculator (I've tried several) and I change the elevation and temp for expected hunting condition, the calc changes the pressure to something like 22.8 inHG. WTH, I check the pressure in Leadville (about 50 miles away at 10200') and it always within a few tenths of where I'm shooting, actually last time we shot it was a tenth higher than shooting location. What gives? Should I not worry about this or should I change the pressure to match what weather stations nearby at higher elevation are reporting?
2. I'm having trouble with the calc matching what I'm seeing on target. I'm shooting 142gr ABLRs using updated G7 BC. I'm shooting 3.5" high at 100 and 2" low at 300. The calc is saying my vel. is 2900+, my chrony is saying 2650, I know 2900+ is not right, but I'm not sure how to reconcile this with the calc. I will be doing actual shooting to confirm all drops out to 800 and there have always been small differences between calc and target in the past but not this much. Any suggestions? (having the same problem with .284 also)

What ballistic calculator are you Using?

 

[pbatesaz]

....
2. I'm having trouble with the calc matching what I'm seeing on target. I'm shooting 142gr ABLRs using updated G7 BC. I'm shooting 3.5" high at 100 and 2" low at 300. ....

At what distance is your rifle zeroed?

 

[Caveman0101]

What ballistic calculator are you Using?

G7, Berger, Hornady

 

[_Windrider_]

G7, Berger, Hornady

No what calculator. Applied ballistics, TRASOL 4DOF Strelok? And do you have a kestrel?

 

[Caveman0101]

No what calculator. Applied ballistics, TRASOL 4DOF Strelok? And do you have a kestrel?

G7 ballistic calc program
Berger's program
both of Hornady's programs
I tried them all, they all do the same thing.
I do not have a Kestrel.

 

[_Windrider_]

G7 ballistic calc program
Berger's program
both of Hornady's programs
I tried them all, they all do the same thing.
I do not have a Kestrel.

The biggest issue I see is you are trying to use a corrected barometric pressure and your calculator wants station pressure. Use station pressure. That’s the pressure where you are physically standing. Using the pressure from Leadville which is corrected for sea level will always give you bad data.

If you are using an iPhone, download barometer plus (it’s free) and that will give you a pretty good station pressure. Keep in mind it’s not perfect because the iPhone barometer isn’t a calibrated machine like a kestrel but it’ll get the job done. Use the MV you know is correct and work from there.

I highly recommend buying a kestrel.

 

[Lowlight]

you need to start from the beginning and look at your process, it sounds flawed.

1. Confirm zero at 100 yards
2. Reset turrets to read 0 \ 0
3. Shoot a group at 600 yards and confirm drop to be point of aim = point of impact
4. Line up software at 600 yards to match using confirmed data.
5. Adjust muzzle velocity to match the computer to the rifle.

As noted you don,t want to use barometric pressure use Station pressure. You lose 1" every 1000ft so your station pressure will read 22.xx ish

For BC you need distance, 100 to 300 is too short the better place to adjust is 800.

Make sure your sight height is correct. Along with other data .

Remember you have to shoot the rifle, it cannot match the computer the computer has to be matched to what the rifle is doing

 

[Caveman0101]

The biggest issue I see is you are trying to use a corrected barometric pressure and your calculator wants station pressure. Use station pressure. That’s the pressure where you are physically standing. Using the pressure from Leadville which is corrected for sea level will always give you bad data.

If you are using an iPhone, download barometer plus (it’s free) and that will give you a pretty good station pressure. Keep in mind it’s not perfect because the iPhone barometer isn’t a calibrated machine like a kestrel but it’ll get the job done. Use the MV you know is correct and work from there.

I highly recommend buying a kestrel.

Thanks, Tac
That is the difference I'm seeing, my station pressure at 7500' was actually 22.63.

 

[_Windrider_]

Remember you have to shoot the rifle, it cannot match the computer the computer has to be matched to what the rifle is doing

This is the key to the whole thing right here and the one thing no one does.

 

[Caveman0101]

That was it, now the calc matches my dope. I'll continue to check it out to 1000 next time I get a chance to shoot. Thanks for the help.

 

[Caveman0101]

you need to start from the beginning and look at your process, it sounds flawed.

1. Confirm zero at 100 yards
2. Reset turrets to read 0 \ 0
3. Shoot a group at 600 yards and confirm drop to be point of aim = point of impact
4. Line up software at 600 yards to match using confirmed data.
5. Adjust muzzle velocity to match the computer to the rifle.

As noted you don,t want to use barometric pressure use Station pressure. You lose 1" every 1000ft so your station pressure will read 22.xx ish

For BC you need distance, 100 to 300 is too short the better place to adjust is 800.

Make sure your sight height is correct. Along with other data .

Remember you have to shoot the rifle, it cannot match the computer the computer has to be matched to what the rifle is doing

Will do sir,
I actually set our hunting rigs up zero at 300 yards. Usually, not a lot of time for adjustment when you happen upon them at less than 300 yards. We did have all this dope confirmed before but changed loads and had to start over, I just don't remember having this much trouble in the past or maybe I forgot about it.

 

[Lowlight]

you want a 100 yard zero you can always dial it up during the hunt,

You have plenty of time

 

[JMGlasgow]

Or dial it up to a 300 yard zero and leave it there.

 

[MakeSawdust]

I know this is a somewhat old post. I use the same rifle to shoot matches and call coyotes. I zero at 100 yds and set the turret to -0.5 mils. I then dial up to zero. Using the zero offset in the calculator I can account for the offset and have a true 100 yard zero (it just isn't zero on the turret). With a half mill above my 100 yd zero dialed on the gun I have a MPBZ dialed on, and I can use the same numbers whether I'm dialing or holding. It allows me to not have to think when coyotes are bouncing around at normal ranges under 300 and makes the number the same for holding or dialing with what is dialed on the gun during hunting. However, it gives me a true 100 yd zero to work from and avoids the shit show of actually trying to zero at 240 or 265 or whatever happens to be MPBZ in those conditions. It works well for me. For guns that do not see any hunting use I do it like everyone else, 100=0.

 

[Dthomas3523]

I know this is a somewhat old post. I use the same rifle to shoot matches and call coyotes. I zero at 100 yds and set the turret to -0.5 mils. I then dial up to zero. Using the zero offset in the calculator I can account for the offset and have a true 100 yard zero (it just isn't zero on the turret). With a half mill above my 100 yd zero dialed on the gun I have a MPBZ dialed on, and I can use the same numbers whether I'm dialing or holding. It allows me to not have to think when coyotes are bouncing around at normal ranges under 300 and makes the number the same for holding or dialing with what is dialed on the gun during hunting. However, it gives me a true 100 yd zero to work from and avoids the shit show of actually trying to zero at 240 or 265 or whatever happens to be MPBZ in those conditions. It works well for me. For guns that do not see any hunting use I do it like everyone else, 100=0.

I might be missing something, sorry if I did.

What would be the difference in setting the turret to zero with 100yd and then just leaving it at .5 up for hunting?

If I’m reading it right, your zero is .5 mil higher than 100.

Or, do you do this because you want to be able to use the zero stop without looking and just run it down to the bottom? If so, that’s pretty cool outside the box way to do that with a turret that doesn’t have an adjustable zero stop.

 

[MakeSawdust]

I might be missing something, sorry if I did.

What would be the difference in setting the turret to zero with 100yd and then just leaving it at .5 up for hunting?

If I’m reading it right, your zero is .5 mil higher than 100.

Or, do you do this because you want to be able to use the zero stop without looking and just run it down to the bottom? If so, that’s pretty cool outside the box way to do that with a turret that doesn’t have an adjustable zero stop.

I do it this way because I want to be able to use holdovers on coyotes that are leaving and only stop for an instant when the turret is set at .5 up and dial for the stupid ones that set on their butt way out there and stare at you. With .5 dialed on 400 yds is a 1 mil hold. I usually range landmarks when I sit down to call and can make a quick guess if I need to. If I'm hunting with a buddy one of us runs the rangefinder while the other shoots. I can use the same card/dope disc/ whatever you please for the same solution. If I sit down to call with .5 dialed on, but my turret is now at .5 instead of 0, now a 400 yd shot becomes 1.5 on the turret or 1.0 in the reticle. I would be working with two sets of numbers. It's easy to remember on the square range, but it all goes out the window when there are two or three coyotes zig-zagging in front of you on stand. If I had ice water flowing through my veins I could probably work any system, but this works the best for me under pressure. It puts the extra thought in the calculations that are done beforehand when there is no stress and removes the need to account for the .5 dialed on (if I were to zero the turret at 100) if I need to hold over because of time constraints.

It also has the added benefit of putting the 100 yd zero at the zero stop on the AMG, but I was running the same system on other scopes before where I could move the zero stop.