Was all good but today shooting low?

[Bravo 4]

It was quite windy and humid compared to the other time. I shot. Maybe that had something to do with it. I have never used the barometric pressure in my dope, just the altitude.

As far as I'm concerned you probably just answered your own question. PB can change at any altitude...altitude will not change unless you move to a different shooting position but PB will change no matter where you are. It can make your drops change throughout the day (as an example), your drops in the afternoon can be different from your drops earlier that morning. Or one day to the next. In my opinion this is a case of bad info put in your ballistics program.

 

[Broz]

As much trouble as you have had, assuming this has all been the same rifle, I would look hard at these things.

Accurate input data into your Ballistic app.

Also the form used to execute these shots. Inconsistent point of impacts often are related to bad form. There is an article I wrote in the ELR forum that could offer some pointers. "The importance of being solid" An uncontrolled platform can often induce point of impact changes.

Jeff

 

[barnesuser28]

As much trouble as you have had, assuming this has all been the same rifle, I would look hard at these things.

Accurate input data into your Ballistic app.

Also the form used to execute these shots. Inconsistent point of impacts often are related to bad form. There is an article I wrote in the ELR forum that could offer some pointers. "The importance of being solid" An uncontrolled platform can often induce point of impact changes.

Jeff

Agreed, i was pulling my hair out trying to figure why my POI were so inconsistent at 1581 yards and traced it back to my form. I guess i should go back and reread that thread.

 

[coyotekiller82]

It was quite windy and humid compared to the other time. I shot. Maybe that had something to do with it. I have never used the barometric pressure in my dope, just the altitude.

Increased humidity is the culprit. Air density is thicker, causing more drop. Next time input the bar press & you'll be closer to your initial POI.

 

[Bigcat_hunter]

Ok so I went back this morning and instead of just using altitude and temp I entered the baro pressure, humidity, temp and altitude. It seems I am sooting much slower then I previously thought(if this is correct). At 2680 fps (not 2750 or 2800 fps like before) my drops are accurate up to 1,100 yards using all the input from my weather station.

I am really hoping this is all correct now. I know I can't trust my chronograph thats for sure. I will go back on a day with lower humidity and try this again with the new velocity input and correct data and see if my drops are still good.

I never realized how much the humidity and baro pressure have on bullet drop way out there. This is all self taught with help from this website so pardon my ignorance on some of this stuff.

 

[bigngreen]

Baro is an essential input, humidity won't change anything at the ranges your looking at, its the most minor input. Make sure to use your baro correctly, station pressure without elevation OR corrected and elevation, some programs allow station pressure and elevation which double downs the input.

 

[Bigcat_hunter]

Bark is an essential input, humidity won't change anything at the ranges your looking at, its the most minor input. Make sure to use your bark correcrly, station pressure without elevation OR corrected and elevation, some programs allow station pressure and elevation which double downs the input.

I am using the shooter app which allows for altitude & baro pressure or "pressure is absolute" which is only pressure and NOT altitude. I used the "altitude and pressure" option. Is that what I should use?

If I use the "baro pressure only" my drop is 1.5 MOA too high.

 

[barnesuser28]

If you use the altitude and pressure option, the pressure is/has to be corrected for the elevation. I use the station pressure as that is what my barometer reads. For 2600 ft ASL my station pressure is 27.00-27.50 inHg depending on the day. At 7000-8000 ft it will be 22.00-23.00 inHg. If you use the corrected pressure, it will be near 30.00 inHg no matter the elevation.

 

[Bigcat_hunter]

If you use the altitude and pressure option, the pressure is/has to be corrected for the elevation. I use the station pressure as that is what my barometer reads. For 2600 ft ASL my station pressure is 27.00-27.50 inHg depending on the day. At 7000-8000 ft it will be 22.00-23.00 inHg. If you use the corrected pressure, it will be near 30.00 inHg no matter the elevation.

Well my weather station measures barometric pressure, not station pressure and my app asks for baro pressure. But the thing I am not sure about is if I should enter the baro pressure AND altitude or just baro pressure with altitude turned off.

 

[Engineering101]

bigcat

If you measure baro pressure with your weather station where you are standing, that is station pressure. I input both station pressure and altitude into my program (iSnipe) because it doesn't seem to work otherwise.

 

[barnesuser28]

The station pressure is the baro pressure, not corrected for altitude. What elevation are you shooting at?

 

[Bigcat_hunter]

The station pressure is the baro pressure, not corrected for altitude. What elevation are you shooting at?

Well I am shooting at 4200 feet but I hunt bears at sea level and elk all the way up to 8500 feet. So I need it to work at every elevation.

 

[bigngreen]

How are you getting your bark pressure?

 

[Bigcat_hunter]

How are you getting your bark pressure?

I am using a weather hawk SM-28 weather meter which reads altitude, temp, baro pressure and humidity.