Range Report Truing Ballistics question....

[jwrowland77]

I was over on The High Road and a person told me to come here and ask.

A little background. All avg MV taken with MagnetoSpeed. I use Ballistic AE app.

I'm shooting a Rem 700 SPS Varmint with the 26" barrel. Caliber .308.

600yd Load:
175gr SMK
IMR 4064 44.5gr
CCI 250
Win case
Avg MV 2709

On my app, it says to adjust up 15moa. I've shot this load at 3 different locations, 3 different states in temps ranging 50-100. When I actually shoot the matches my up adjustment is only 13-13.5moa. So a 78"-81" drop instead of a 88"-90" drop like app says it should be.

I'm using litz g7 values.

1000yd load:
175gr SMK
2000-MR 47.5gr
CCI 250
Lapua case
Avg MV 2750

App says to up adjust 35 MOA. Actual MOA is only 31.5. So instead of a 350" drop I'm only getting a 315" drop.

I've shot both loads in all types of conditions during matches. Just trying to figure out why it's not dropping as much as it says it should. Not that I'm complaining, just trying to figure it out is all.

Cool site too. Hope to learn a lot here.


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[Rthur]

I'm going to say adjust your velocity up at little and see what it comes up with. I would suggest 25fps at a time and see how close that matches your dope. Also another problem I don't see what DA (Density Altitude) listed as an input. Why do you have two different loads for 600 and 1000? Are these FTR loads? It has been my experience that some fine tuning is required to get them very close to observed dope.


R

 

[jwrowland77]

Yes they are FTR loads. It automatically inputs the altitude and other weather items for me. When I correct the velocity using the app, it bumps it up to something like 2850fps which is just down right crazy. I love that ballistic AE app.


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[Fredo0621]

I'm the guy who told him to come and ask the question here because of the wealth of knowledge on this board. I'm completely baffled by this and would love to know if someone can pinpoint this.

 

[wnroscoe]

First, you need a Kestrel or other accurate environmental measuring device. I use a Kestrel 4500NV and find it does all I need. Stop letting the device select meteorological settings from another location, it's never the same where you're at.

The accurate velocity of your load/ammo is needed but, not a deal killer if you don't have it.

Record your actual data from your shooting sessions ie actual bullet drop/dope. You'll also need to record the meteorological data while shooting, the Kestrel will give this data. Now, in Ballistic AE start a new trajectory with bullet, weight, velocity. meteorological data etc. beside the velocity box you'll notice a small ">" sign, press this and another screen opens that will allow you to enter your actual POI in relation to your POA, high or low. This truing feature needs to be ran at 3-5 midrange distances at a minimum to be effective. Once the data has been entered select the units of measurement and "correct velocity" I also use "Drop is Relative"

This will true the app to your ammo. We've tried this on several rifles and it works with out fail but, and I say but, nothing replaces trigger time to confirm the dope. Your rifle and ammo need to be spot on and dead ass accurate to give solid and repeatable results.

 

[jwrowland77]

A Kestrel is on my short list of items to get. Very short list.

I absolutely agree about the trigger time. I've almost gotten to the point where I just use my log books where I record weather conditions and whatnot from my matches. I do have log books from all three spots I've shot at just so I can calculate what my drop (which I know) and what my windage should be.

Looks like I'll have to get the mid-range POI and make a new favorite with my load and actual drops at the mid-range area and recalculate.

This was kind of a sitting at my reloading bench and wondering, hmmmm why do my log books say something different type thing. I always go with the log books since they're the most accurate.

Thanks again. I'll have to try and get out this weekend and do the midrange POI and plug them in and see what I get and see if they compare to my log books I keep.


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[jwrowland77]

Actually, I'll probably have to wait a bit before hitting the local range. It was affected by the tornado that came through this past Sunday. Knocked the power out there. Lots a clean-up to happen first before that gets fixed I'm sure.


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[EOD350]

wnroscoe is right on here. You will also need to true the elevation turret to the program. That is at the mid-ranges roscoe is referring to. I have observed data changes as the weather changed while I was actively shooting. The 4500nv is better for this as it updates as the changes occur.

 

[damoncali]

Garbage in garbage out. You need to verify every input to the best of your ability. Velocity (runt he numbers for your high number and your low to get a range). Use a good BC (probably G7). Atmospherics matter - guessing will put you off a little. May as well enter an accurate angle of fire as well if you can get it. And is it exactly 1000 yards? you can get a decent verification with Google Earth if you don't have a range finder.

If you carefully input everything you can as accurately as you can, I think you'll be a good bit closer. I get within half an MOA usually without resorting to tricks to "true" the calculator.

By the way, if you think Kestrels are too pricey, one of the Leica 1600 range finders (you have to check, one does, and the other doesn't) also gives atmospherics (temperature and pressure at least, which are the two that matter) as well as angle of fire and range. A lot of people don't know that.

 

[jwrowland77]

I haven't thought about high range and low range. I generally use gps for elevation and whatnot. It gives me several particulars.

As far as I know, range finders aren't allowed at a match, I know range finding scopes aren't. I'll have to take a look at Google Earth to verify distance.

I use the LOS adjustment to make sure. I'll have to verify distance on Google Earth and report back.


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[jwrowland77]

Truing Ballistics question....

I verified distance for Tulsa using an app that I have that uses satellite image and the place in Tulsa is 539m so like 589yards. Just shy of 600. When I looked at my calculations in the Ballistic AE for 575 it gave me 13.1. Add another few yards to that and I'd be at 13.5 which is what I'm actually seeing.

Thanks for the idea of verifying distance. So using my input, and the weather and whatnot on the app and getting the calculations are actually correct. It's the distance that's not quite 600yds. It's probably the same thing at the other two venues I shoot matches at.

It wasn't a big deal. I know where to dial in it by looking at my match log books I keep, it was just more of a why. It's the accountant in me I guess. Lol


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[jwrowland77]

Verified distance in Memphis and Little Rock using google earth and all three were the same at the "600"yd distance. The 1000yd though, was 998yd. That one may just be the light updraft that we normally get off the 600yd berm


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[Capt Academy]

Tagged

 

[BryanLitz]

I highly suspect it's scope tracking error in this case, and not a ballistic calibration issue.

In the case of your 600 yard dope, the error is 13.25/15=0.88

In the case of your 1000 yard dope, the error is 31.5/35=0.9

It seems like your scope is moving about 11% too much (assuming other aspects of your solution are accurate).

You would need to do the tall target test at 100 yards to confirm this (http://appliedballisticsllc.com/m-ftr/ABDOC123_TallTarget.pdf), but as things are, if you used a sight scale factor of 0.89 it would put you on at both ranges. In other words, multiply the output of your ballistics app by 0.89, then apply that to your scope.

At 600 yards, you would get: 15*0.89 = 13.35
at 1000 yards, you would get 35*0.89 = 31.5

These are both within a click of what you actually used.

The Applied Ballistics mobile app accepts the scope correction factor as an input, and automatically corrects your raw calculation to account for scope tracking error. I don't know if Ballistic AE has this feature.

I would confirm scope tracking at 100 yards to be sure, but it really seems like the culprit in this case since the same correction factor works for both 600 and 1000 yards.

Take care,
-Bryan

 

[jwrowland77]

I'll get and do a box test once our range opens back up from the tornado damage and double check it.

Thank you sir, I'll check that out and report back



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[BryanLitz]

I'll get and do a box test once our range opens back up from the tornado damage and double check it.

Thank you sir, I'll check that out and report back



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For clarity,
The tall target test isn't the same as a box test.

The tall target test measures how much your scope *actually* moves the reticle compared to how much you dial.

So if you dial 30 MOA at 100 yards, you would expect the POI to move 31.41". If the groups move more or less than 31.41", then you have to account for the error.

I only mention this because a box test is sometimes just checking that the POI returns to zero after making adjustments. The tall target test is looking at the exact amount of scope movement in relation to what is dialed.

-Bryan

 

[jwrowland77]

Ah ok. Gotcha. Learn something new every day.


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[jwrowland77]

Got to thinking, I don't know if I have anywhere I can do this test. The targets at the state ran range aren't this tall because there's a certain area on the holder you have to place your target. They don't allow you to place your own holders out there either. Reason they started doing it this way is because they had issues with ricochets.


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[damoncali]

Got to thinking, I don't know if I have anywhere I can do this test. The targets at the state ran range aren't this tall because there's a certain area on the holder you have to place your target. They don't allow you to place your own holders out there either. Reason they started doing it this way is because they had issues with ricochets.


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You can get creative - zero the rifle, then move the target down before you put the elevation on the scope. Kind of a pain, but you can still get it done.

 

[jwrowland77]

You can get creative - zero the rifle, then move the target down before you put the elevation on the scope. Kind of a pain, but you can still get it done.

With the way their holders are, there's not enough room to move the target down far enough. I really wish their holders were like other ranges I've been too. Their holders are made from 2x2's with cardboard backing and the legs slide over these pegs. The frame is about 2' wide by about 30" long. I'd have to zero then move it down to the frame while it blew in the wind. Then I might hit top of frame.


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[damoncali]

With the way their holders are, there's not enough room to move the target down far enough. I really wish their holders were like other ranges I've been too. Their holders are made from 2x2's with cardboard backing and the legs slide over these pegs. The frame is about 2' wide by about 30" long. I'd have to zero then move it down to the frame while it blew in the wind. Then I might hit top of frame.


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Maybe you can rig up your rifle in a really stable rest somehow and just dial the scope without moving the rifle and see if it matches up with a pre marked target (draw a line, and mark 1 MOA, 2 MOA, etc) without shooting. Probably easier said than done.

 

[Aimsmall55]

Got to wondering ... Exactly what kind of scope is it and what mount and rings are you using. I read the whole thread but I didn't see it

 

[oneshot.onehit]

Just a little info I posted for another not long ago


Calibrating your scope to your Ballistics program

It's a common practice to calibrate any new scope prior to mounting on a rifle.

My setup used prior to mounting a scope on a rifle

This is done in an area that has been measured to an exact 100 yards by means of a measuring tape then have a 72" carpenters rule hung on a wall that is plumbed a true vertical. On the opposite end of the measured 100 yards is the scope mounted in a one piece scope mount held in a vice solid with reticle squared with the ruler. Now with the crosshairs at the top of the rule dial the turret and see if it ends up correctly as dialed in either moa or mils.

The amount of error will increase as you dial the full length of the rule, take note in the amount of error as you continue.

This is a result of how aggressive or not the the threads are milled at. This does not matter if its a Night Force Schmitty, Vortex etc.

You then can go into your program and do a correction factor adjustment in your ballistics program to correct the difference in adjustment needed.


Cheers