Indoor range zero- be gentle

[Shootinsurveyor]

should I hold atmospherics from the indoor range (70 degrees, etc) or should I just use the info populated into the app from the closest weather station? I assume pressure would be the same, but this time of year temp is a huge difference. Flame on if you must, just a honest question

 

[AIAW]

Ideally you'd use a weather meter like a Kestrel and pull temperature, station pressure OR DA from it. DA is going to involve temperature automatically, unless you need the temp for powder burn rate manipulation.

The pressure may be the same inside the range, so you could just plug that in manually. For a zero it's honestly not going to matter, within reason.

I would focus on powder temperature deviation more than external ballistics aspect.

 

[308pirate]

How fucking long can an indoor range be for any of this shit to matter?

Seriously, someone help me understand this

 

[AIAW]

Hahaha, I thought the same thing!

I think he is referring to putting "zeroing condition" data in his ballistics app.

 

[Shootinsurveyor]

Just thinking about having the right info from the start so when I do shoot longer than 100 in say Montana vs Virginia

 

[Conaso]

308pirate - Do you think you can offer your eclectic advice without being so vulgar and disparaging?

 

[howe0001]

Station pressure over barometric pressure. Station pressure of where you are at the time you are shooting is the pressure info you want (also called absolute pressure). Barometric Pressure is a weather term and is the location you are at, calculated to sea level, so unless your calculator reverse engineers the barometric pressure of your weather station in your area by using some inputted altitude, always opt for "station pressure" or "absolute pressure" when you have the chance if you don't know your altitude.

That's my 1.33 cents worth.

http://appliedballisticsllc.com/ufaqs/barometric-pressure-vs-station-pressure/

 

[CRT2]

should I hold atmospherics from the indoor range (70 degrees, etc) or should I just use the info populated into the app from the closest weather station? I assume pressure would be the same, but this time of year temp is a huge difference. Flame on if you must, just a honest question

Well, if you are going to shoot indoors then use indoor range info. Me, I would reconfirm/attain data outdoors.

 

[308pirate]

Just thinking about having the right info from the start so when I do shoot longer than 100 in say Montana vs Virginia

When you go someplace else with radically different temperature or elevation, enter the weather data for that place then. Of course you don't keep the atmospherics from where you were.

BTW, do this as an academic exercise

1. Make a list of the weather variables that go into your ballistics software
2. Pick one variable
3. Start changing that variable in reasonable increments (for ex change temp in 10 deg increments
4. Start comparing what those changes do to your dope
5. Think about that change in dope compares to the target sizes you normally shoot
6. Think about that change in dope compares to your shooting ability

The point is to figure out how big of a change to any of the common atmospheric variables has to happen before you need to worry about your dope

The people who obsess over every degree change in temperature, or every hundredth of in Hg change in pressure are probably worrying about things that don't matter.

I now know how much to pay attention to atmospherics because of the above, verified by actually shooting in radically different conditions over the course of the four seasons; and keeping a log book.

Yes, keep a log book/data book. A ballistics app in your phone is no substitute for knowledge that you can refer back to and make intelligent inferences from. Not to mention a data book and hard dope (laminated cards) ALWAYS work.

 

[Rocketvapor]

You forgot local gravity.

 

[TimK]

Zero conditions are negligible if you are using a 100y zero. Prove it to yourself by entering zero conditions of 0 DA and 10,000 DA. Check to see how much difference it makes on your firing solution at 600 or something.

 

[Ledzep]

Lighting will be your biggest enemy. Don't be surprised if indoor vs. outdoor produces a zero shift.

 

[TimK]

Lighting will be your biggest enemy. Don't be surprised if indoor vs. outdoor produces a zero shift.

I've heard that mentioned before but don't personally have that problem. I zero everything indoors, and mine seem to correspond well to confirmation outdoors.

The bigger problem for me is mirage. It doesn't take many shots at all for me to get mirage off the barrel that's so bad I have to wait. I've taken to bringing a small battery powered fan to the indoor range with me. I set it up to blow the mirage away. It sorta works.

 

[DocUSMCRetired]

Atmospherics themselves (other than Aerodynamic Jump), with all things being equal (including things like muzzle velocity) have no effect on the zero at 100 yards. Also neither do changes in elevation. What does have an effect on your zero:

1) Aerodynamic Jump - Happens at the muzzle.
2) Position and Surface the rifle was zeroed on - Has an effect on how the rifle was held (your fundamentals), and the recoil impulse.
3) Powder Temperature Sensitivity - A more stable powder will not see much effect (if your powder shifts .2 fps per degree it will take quite a swing in temp to change your zero), where as unstable powders which can see as much as 3fps per degree Fahrenheit are obviously going to effect your zero.
4) Lighting (as mentioned in another post) effects like mirage can certainly affect perceived zero (as it optically changes what you see). But that is a different discussion.

In short atmospherics don't affect your 100 yard zero because the bullets flight time is too short when it comes to actual bullet flight. But how, where, certain component choices etc. when you perform that zero can affect it.

 

[Ledzep]

I left a camera on a cliff side one day last year, time lapse photography every 10 minutes for.. I forget... 5-6 hours or so. It was a sunny day that turned partly cloudy. As you scroll through the photographs on the SD card, you can watch the image shrink and grow with the corresponding ambient light. That's fair enough-- the air acts more or less like a lens and with more light there's more heat, change in heat changes density, change in density changes index of refraction--> bend light.

What tripped me up was when I located the "center" of the photographs (they're all the same H*W pixel count so I found the center through that), there was also vertical movement. This is about a 10x zoom lens, roughly 450yd away. Tantalizing subject because what our eyes send to our brain is BS to begin with, so there's a weak link, and most everything that I would think to use to measure the effect is also affected by light and/or temperature so it's very hard to isolate causation. And to be honest, the physics surrounding radiation are not my strongest point. The camera auto-gates itself, so aperture diameter and exposure time can be different between pictures, the lens body might expand or contract with temperature, etc... It's hard to know exactly how much the image is actually shifting and how much is instrument error.

Nonetheless, I think this same (or similar) phenomena can be seen through heavy enough rifle platforms or rigidly mounted optics when looking through mirage. The fixed target can move around considerably on the reticle. Anyway... curious. If you look into guys studying space, they never look below 45 degrees because you start to look through enough atmospheric lens that either the clarity or position is distorted so badly it's not worth your time.

 

[wade2big]

?

 

[Snuby642]

I think the op is zeroing his ballistic app at the indoor short range.
So he can save the data and use that as his standard?

My ap will not save original weather data but I do in my book.
It's just a reference none of the envirmentals matter much indoors or at 100yds.
Exceptions I have found are sv 22 lr. And 300blk subs.

Powder temprature change from outdoor cold locker and warming or stored hot,
Texas hot then brought indoors and cooling. And barrel temps as well on the 22lr sv.

I have a powder temperature refrance for a base on the ammo in the app, nothing else.

 

[Shootinsurveyor]

Snuby got it right. Just worried about variations from the environment I zero in when I actually go shoot outside. It’s really just a mental exercise of knowing how to use my software as well as possible.