Cannot get Kestrel w/ AB to True to Actual Dope

[gamecock525]

Took a long range course this weekend and we had targets at 100, then 200 to 1300.
Everyone zeroed at 100. Environmentals (according to Kestrel 5700) were:
89F
29.24inH
59% RH
3059 DA

Shooting Prime 130g 6.5 Creedmoor in Ruger RPR with factory barrel and SilencerCo Harvester.
I had previously chorno'd these rounds in this configuration through a Magneto V3 at 2850 w/ SD of 9.

Kestrel Results vs. Acutal
200 yd - 1.5 moa lowered to .75
400yd - 6.25 lowered to 5
600yd - 12 lowered to 11
800yd - 18 lowered to 17.25
1000yd - 26.5 perfect
1200yd - 36.5 held at 38.5

Dope was confirmed the following day at similar environmentals within .25moa.

When I true the MV in the Kestrel based on 1k (because I was having to hold over on 1200 since I ran out of elevation on my scope at 36 moa), the range card does not even come close to what actual dope was.
What can I do?
Any thoughts on why the discrepancy?

 

[Nik H]

Have you tried a similar experiment without the suppressor?

I use the same ammo in similar conditions. I am shooting an AI AT with a 24" Bartlein barrel. I just looked at my DOPE to 600 yards that I corrected. Initial numbers were from my Kestrel as well. Difference between what the Kestrel gave me and what I recorded was about 0.1-0.2 MILs apart....very close to predicted at all ranges (200-600 yards).

 

[gamecock525]

I have not, since I generally only have access to 300yds.
I would think, though, that if I trued at the farthest distance, it should reciprocate backwards. I tried trueing at 1k, 800, and 600. The only "correct" figure was what I trued. Nothing else matched.

 

[_Windrider_]

I have not, since I generally only have access to 300yds.
I would think, though, that if I trued at the farthest distance, it should reciprocate backwards. I tried trueing at 1k, 800, and 600. The only "correct" figure was what I trued. Nothing else matched.

What were the conditions in which you got that MV?

 

[gamecock525]

Good question. Don't have DA and pressure off hand, but I know the temp was in the low 70s

 

[_Windrider_]

Good question. Don't have DA and pressure off hand, but I know the temp was in the low 70s

AB is more accurate the more readings you have at different temps. For example ( totally made up numbers for illustrative purpose), if you had 1000 fps at 80 degrees and 500 at 40 degrees, it would know the average change in fps per degree and would be more accurate. In your situation, I believe this is what's missing. You have one reading at one degree and we're shooting in different conditions. It can't estimate as accurately what your MV is in current conditions.

DocUSMCRetired , anything to add?

 

[DocUSMCRetired]

^ Is correct essentially. Since you are off nearly linear at all distances I would look at a couple of things:

1) Are you using the G7 or CDM?

2) The MV.

3) Have you checked your scopes turrets?

 

[Sixfivesavage]

How many rounds on the barrel? May be speeding up.

 

[gamecock525]

1 - using G1
2 - I will re-chrono at now warmer temps
3 - Yes, turrets are verified at true MOA

I had 247 rounds on the barrel. After the class I'm at about 370 (haven't tallied my final round count yet). I'm thinking I may just give it a good cleaning and start all over.

 

[_Windrider_]

1 - using G1
2 - I will re-chrono at now warmer temps
3 - Yes, turrets are verified at true MOA

I had 247 rounds on the barrel. After the class I'm at about 370 (haven't tallied my final round count yet). I'm thinking I may just give it a good cleaning and start all over.

I wouldn't if I were you. I have a RPR that has been spot on withAB from day one. It took time however gathering MV at different temps in order to get AB to be more accurate.

Try putting this in the kestrel gun profile and see if it matches what you got. If not it's a good place to start with your base of 2850 @70f:

2793 @40f
2808 @50f
2827 @60f
2850 @70f
​​​​​​​2879 @80f 2915 @90f

from here you can correct as you get better real data but this about 2ish average change in MV per degree.

 

[CharlieNC]

Dismissing the 1200 due to your uncertainty. When you trued at 1000, ALL the other distances are off .75 to 1.0 mil. This suggests the 1000yd may be off. Try adjusting mv to get the other yds correct.

 

[djarecke]

If AB isn't truing, it's not a problem with the solver, it's some type of input error. Here are a few things I see frequently:

1. Improper input of wind conditions from actual shooting conditions

2. Improper ranging to targets

3. Not measuring scope height correctly

It doesn't really matter what your muzzle velocity is (unless you want an educated guess for your first MV input), so don't bother with the chronograph. Check your zero, record your actual dope to the furthest target you can shoot (and remain supersonic or transonic) and use the "TRUE MV" feature. Finally, shoot an intermediate distance to verify it. You should be good at all distances if this is done properly.

I've done this at least a dozen times with various platforms and the solver is almost always 100% correct at any distance.

 

[Saf3sh00t3r]

^^^ what djarecke said...he has helped me in the past... anyway...my issue in the past has been wind in relation AerJ, that will typically throw off your dope. Mine once my inputs are good the DOPE is right on to 1100.

Set one of your wind values to zero, try again this will remove AerJ from the solver for now as a test...aerodynamic jump or crosswind jump is a true phenomenon, but turning it off helps to verify drops.


Sent from my iPhone using Tapatalk

 

[poison123]

Its also possible the entry in the kestrel could be slightly corrupted......

 

[d_train821]

Try running it on G7 or with the Norma Diamond 130 DM

 

[6AYoteHunter]

What is your scope height? Center of bore to center of scope tube?

 

[Rauch Precision]

Scope height will not create bad dopes but will make for an inaccurate point blank range. You can play around with that on your kestrel and change the scope height, doesn't really make that much difference. The big question I have for you is do you have MV temp on and if you do then do you have at least 30 degrees between your temperatures. If you do not then you will get bad dopes. My only other guess is that your ammo is temperature sensitive and you are seeing the difference in MV from the temp when you chrono'd and where you shot.

 

[morganlamprecht]

scope height can make a big difference unless youre shooting at giant targets...

my scope height is 2.45", 130 hybrid dope to 1000yds is 8.3 mil at 0DA
if i leave it 1.5" (default in this particular app), its 8.6 mil...it matters if youre actually trying to true things up correctly, and not shooting at full size ipsc's

 

[BallisticSam]

You could try to correct the velocity at a shorter range like 500yds not 1k if I'm reading that right. I use the GeoBallistics app and Weather Flow weather meter and I have trued my RPR with 140s, and 123s out of the same rifle at 500 and it has been spot on for every distance from 100 to 1k. Not like over a little here or under there but spot f'n on. Now, when I first got the hard ware I tried the velocity calculation correction at 300yds and it put my 140s at a MV of 1800fps, Then I re-read the instructions and it says it works better at distances past 300. 500 worked perfect. I would imagine any farther and you are throwing in more variables to the shot your trying to correct from. Yeah you can hit that target at 1k, but you can hit it even better at 500 with less error in wind and other things effecting the bullet. I have since noticed from different threads on here and youtube vids that others shooting the same rifle "rpr 6.5creed" are having the same data for as me. Like the vid of Ryans Range Report from youtube of him shooting the RPR to 1200 and his data matched mine in the Geoballistics app to the mil. I have since found no need for a crono other than to watch for erratic velocities and sd from load development. Just seams more fluid to let the hand held tell you what your rifle is doing than telling it what to think its doing.

 

[morganlamprecht]

You could try to correct the velocity at a shorter range like 500yds not 1k if I'm reading that right. I use the GeoBallistics app and Weather Flow weather meter and I have trued my RPR with 140s, and 123s out of the same rifle at 500 and it has been spot on for every distance from 100 to 1k. Not like over a little here or under there but spot f'n on. Now, when I first got the hard ware I tried the velocity calculation correction at 300yds and it put my 140s at a MV of 1800fps, Then I re-read the instructions and it says it works better at distances past 300. 500 worked perfect. I would imagine any farther and you are throwing in more variables to the shot your trying to correct from. Yeah you can hit that target at 1k, but you can hit it even better at 500 with less error in wind and other things effecting the bullet. I have since noticed from different threads on here and youtube vids that others shooting the same rifle "rpr 6.5creed" are having the same data for as me. Like the vid of Ryans Range Report from youtube of him shooting the RPR to 1200 and his data matched mine in the Geoballistics app to the mil. I have since found no need for a crono other than to watch for erratic velocities and sd from load development. Just seams more fluid to let the hand held tell you what your rifle is doing than telling it what to think its doing.

this is the right track, but its really simple with a chrono (a good one, like a magneto)

1) make sure all user inputs are correct
2) get muzzle velocity
3) shoot targets in the 5-700 yd range and tweak velocity to match vertical (if youve done everything right it shouldnt take much truing at all...believe im running the the magneto velocity +/- 10 fps in all my barrels rifles, like 15 different loads, ive gone straight from the 100 yd line with only velocity from a chrono to a match more than one occasion)
4) shoot at targets from 700-end of super sonic range and tweak BC to align

this method works in any decent app, kestrels, etc and should take less than 20 rounds

people forget about the BC, they just plug into whatever is advertised or in the app...doesnt always work that way, even different lots of the same bullet can have BCs different enough to cause decent error at 800+ yds

 

[Holliday]

I use my 5700 AB almost exclusively with my .308 out to 1200 yards. (I know .308 but I like to shoot a lot and it's cheap).) My dope has been spot-on. There is no question the 5700AB has allowed me to shoot better than I ever would have without it.

Anyone who who knows me knows I was one of the first 5700 AB purchasers and when through some pains n terms of its newness to the market and really understanding its philosophy of use etc. Software/firmware updates and ABs support have taken me to being a HUGE fan. I'm just so glad I bought this thing.

One thing that can be tricky is making sure the settings are all correct. When shooting if it is laying in the sun next to me on the mat. I go into "environment" swing the unit over my head (replace the landyard w/ paracord as the original will come apart!!!) with "update" switched on. Then when I am confident that I have the ambient air temperature I switch "update" to "off". I've been shooting on a 70 deg morning with the Kestrel reading in the 90s from solar heat-soak. Then in a couple hrs I do the same. (Doc correct me if you see anything wrong here)

Also make sure you have the most current firmware. In the past there have been some bugs effecting settings. Make sure that when you upgrade the firmware you pour through your settings meticulously because they will often be reset or changed.

Finally comparing to other ballistic programs can be tricky. Often, if there is a disparity, I find something like my environmentals are not lined up correctly. I use density altitude in other apps and you cannot directly set DA in the Kestrel. Also if you are using powder temp differentials on the Kestrel, be sure you either switch that "off" or properly account for the MV shift in other apps.

 

[mojavejim]

Is your scope tracking correctly ?

 

[Long Range 338]

It seems easy to say but read thru Doc's posts in this section, he explains many facets of this better than the rest of us can, specifically for the Kestrels running AB..... just follow his posts. DocUSMCRetired

 

[gamecock525]

Thanks for all the inputs.

 

[Coyotekiller64]

Try truing b.c. numbers,my 6 b rnorma and6.5 gap both shot first through lab radar was perfect from 100 to 1000yds. ,but had to lower advertised b.c. numbers 1100 on out till it all lined up .B.c. numbers adjusted about 2 lower did the trick .

 

[_Windrider_]

You can do all the truing / curve fitting you want.. some will seem good. But never adjust BC before truing velocity.

https://www.snipershide.com/shooting/forum/...vr#post6291944

Serious question here.

A muzzle velocity published by manufacturer or litz or whomever is generally an average at a specific MV (especially by manufacturer as published BC is at the published MV). If I true my MV then true my BC, am I not then untruiing my MV? If you have a known MV, you true BC. If you have a known BC you true MV. But I can't reconcile how you do both. If I use a BC of .350 for projectile x and my app says use 10.3 mils at 1k and I actually needed 10.5 and I true my MV to show 10.5, if I now change the BC won't it change my drop at my now trued MV? Help me understand and this. Am I being dense or am I missing something? I have a chrono and keep accurate data on MV at different t temps, so I have never needed to true my MV, but I do have to tweak the BC, I have never done both.

 

[DocUSMCRetired]

Serious question here.

A muzzle velocity published by manufacturer or litz or whomever is generally an average at a specific MV (especially by manufacturer as published BC is at the published MV). If I true my MV then true my BC, am I not then untruiing my MV? If you have a known MV, you true BC. If you have a known BC you true MV. But I can't reconcile how you do both. If I use a BC of .350 for projectile x and my app says use 10.3 mils at 1k and I actually needed 10.5 and I true my MV to show 10.5, if I now change the BC won't it change my drop at my now trued MV? Help me understand and this. Am I being dense or am I missing something? I have a chrono and keep accurate data on MV at different t temps, so I have never needed to true my MV, but I do have to tweak the BC, I have never done both.

If you have a known good BC, and you true your MV then the prediction should be correct out to that point. But, if you have a bullet that has a significant amount of variation from the BC you are using for the prediction, there will come a point where the DSF needs to be corrected for that variation. You can avoid this all together by just not using BCs at all, and using CDMs instead.

You can think of it like a car. A new cars window sticker has a fuel mileage rating for highway. Say "24 mpg". Well that is true, but maybe only at 60 mph. If you are going 85mph chances are you are not getting 24 mpg, you are getting more like 21. BCs are the same way. They are only 100% true at the specific velocity they tested at, and they do change as the bullets velocity changes. Which is why using the correct form factor is so important.

 

[_Windrider_]

I should have put in that all scope truing (Tall Target type test) and correct sight over bore has already been done as essential step one, plus the ability for the shooter/system to land on targets, with small groups.

OK, the very next thing you have to believe is your bullet impacts. √ sounds like you got that done.

What I am saying is that the MVs be it off a Labradar, Magneto, Ohler35, acoustic or optical NEED TO BE CONFIRMED by the bullet drop. In order to do this, the shooter really needs to make sure (most do not) that range is absolutely perfect, the groups centers on target are measured not estimated. In other words you need to be really accurate here if you hoping for near click accurate predictions from the calculators.

In the first several hundred meters out to 300-400 depending on the speed and the round, BC makes very little difference on target unless you really get carried away with the adjustment. But the tinniest error in MV does. Being meticulous in your drop confirmation most often than not will result some MV adjustment. Once this is done, you almost always find the the BC adjustment a needed at lets say 900m is MUCH less.

This all works for two reasons, gravity is constant and BC takes a while to scrub off and speed. What you end up with is most cases more accurate supersonic curve. Now if you are shooting into trans space for some time (distance), AB then has you step the BC with their provided truing distances in trans or with programs like FFS and CB offering anther approach to bending that part of the curve..

While accurate (meticulous) drop confirmation and system vetting is more work that most people can or are willing to do, and you most often "can getaway" with short cuts, if one is really trying to get the curves to work the best they need to ensure all is done in the correct sequence. You really start seeing this as/if you get into ELR were things can go way south of the intended curves, even the custom drag models.

So assuming the shooter/system, range and POI are 100% vetted: Drop confirm to adjust dead on, (not a partial click) out to 300-400 (round dependent), then BC if still needed.

Again, you can get away with a lot, it just if one starts getting anal about why a the curves aren't behaving as planed, then making sure the building block details are true really help if your splitting hairs.

The zero range is a critical piece and it's not so much that many of us go to a range that claims to be 100yds and we zero without confirming it from our exact FFP, it's that many shooters call a 100 yd zero that groups perfectly at .5 MOA good to go as a 100yd zero even though the group is lower or higher than your POA. Because of this it's not actually a 100 yd zero. This is the first error that most shooters introduce into the system. If it's low, you actually zeroed at a distance longer than 100 yds, could be a 110yd zero and vice Versa if it's higher.

I get all that. But let's assume I am exactly at 100 yds. Confirmed. GPS, LRF and tape measure exactly 100 yds to the turret. I have a known MV I shoot and I hit .2 mils low. So I dial up .2 and now I'm dead on (all this assuming I've done tracking tests and all the other troubleshooting). If I change my MV from what I know is real if I then also change the BC I've just untrued that MV. It's simple math. You can only adjust one or the other but not both unless you do what DOC said and use a CDM and take BC out of the equation. I understand what you are saying with DSF and agree that inside 600 or so (caliber dependent) there is no need to change BC. But BC changes as MV changes. So if you change both you aren't truing anything you are actually skewing it further. Now, that's not to say you can't develop your own BCs and velocity bands like AB does in their books I just don't see how changing both gives valid feedback. A shooter should know their MV, the BC should adjusted to reflect real world at given ranges not an average over what distance a manufacturer used.

 

[_Windrider_]

If you have a known good BC, and you true your MV then the prediction should be correct out to that point. But, if you have a bullet that has a significant amount of variation from the BC you are using for the prediction, there will come a point where the DSF needs to be corrected for that variation. You can avoid this all together by just not using BCs at all, and using CDMs instead.

You can think of it like a car. A new cars window sticker has a fuel mileage rating for highway. Say "24 mpg". Well that is true, but maybe only at 60 mph. If you are going 85mph chances are you are not getting 24 mpg, you are getting more like 21. BCs are the same way. They are only 100% true at the specific velocity they tested at, and they do change as the bullets velocity changes. Which is why using the correct form factor is so important.

I totally get it, that's why you guys have velocity bands in the books. MV and BC are directly proportional. If one goes up so does the other and vice versa. Bit if I true my MV and my BC didn't I just untrue that MV? I would have to retrue it to make my drop correct from what I actually saw them my BC is now off? The key is to know your MV. Without that I think you are lost.

 

[_Windrider_]

Look - your making to much out of this. I don't care what "DOC" said. More over, your not understanding what he said. DSF (is a trans curve bender) you still need to do the basics BEFORE going on to DSF etc. or drastically fucking your BC as most are very close from the factory. Further, more CDM's can't use them if your MV is off..

Yes, the assumption is that you can shoot and your ammo is good.

1. you need to know your exact sight over bore
2. you need to know your zero distance is correct.
3. you need to either adjust your scope perfectly to that know zero distance OR create a zero offset.
4. you need to know your exact distance with a tape (not a range finder) to do a Tall Target test. Sorry but that is how it is.
5.you need to create a scale based on that.
6. you need to drop confirm MV at shorter ranges as stated-- thats the speed, not changing the BC or drag curve.. Distance and group offsets are what is key here..

These are the basic building blocks needed for any calculator


or you can keep doing the what your doing.. mybe get a BDC reticle and call it a day

Dude, I'm just trying to wrap my head around this. I'm asking questions cause I'm trying to validate what I think I know. We all do this a million different ways. What I'm trying to understand is a new concept to help me improve.

ive been using AB Mobile and Analytics for a few years now. I use DSF. I have just never trued a MV and trued my BC. I've only done one orr the other. I'm trying to understand how doing both works. That's it.

In the meantime I'll keep on keeping on. I won't ask anymore questions. Thanks for the help, I appreciate it.

 

[secondofangle2]

I've been through this. If you get lucky, it's easy. Oftentimes it's not easy, and you have made some unnecessary assumption in your measurements. It actually takes HOURS to properly do. Here's what I suggest:

1.) Measure with a tape to the 100 yard target and take into account (as stated above) whether POI === POA exactly.
2.) Make a tall target, say 8 feet tall and check your scope tracking. I use 2 4-foot rulers screwed to a long board. Doing it over a shorter interval is too imprecise. This is also why you need a tape to the 100 yard target, do the math and see what happens when you're off a yard when you're doing your reticle truing. You will miscalculate errors significantly.
3.) Make sure your scope is as perfectly level as possible, also with a 100 yard plumb bob - closer than 50 yards and you cannot detect small differences.
3a.) measure scope height (as stated above)

Just that will take a couple of hours to get it right if you are meticulous about it.

4.) Ranging at longer targets (as stated above) is complicated by beam dispersion (eg ranging the sloping hill behind the target). I agree with ranging a vehicle or other large reflective target with the laser on a tripod NOT handheld. COnfirming with GPS if possible is another option for the longer ranges.
5.) MV variation is overlooked and assumptions are always made about it. Now that I use Labradar for every range session, I have noted that from day to day the SAME load can vary by 50 fps even when temps are relatively constant. Don't ask me why, it's just an observation. It is useful to always use the Labradar to see if your last velocity is the current velocity. Much can affect this - scale zeroing/variability between reloading sessions, neck tension variation, lot variation in powder, barrel temp, ambient temp. As your barrel/chamber heats during long strings, or your ammo sits in the sun, etc.
6.) Use doppler radar BCs from hornady for example or Litz's G7
7.) Yes, go and MEASURE how far your group CENTER is from POA and account for that in your truing. As stated above "It's on the IPSC" is insufficient
8.) Check your level between shots
9.) Recheck your atmospherics during your shooting session. Temp and baro pressure can change significantly over several hours in an afternoon. Document the changes when you're truing
10.) Account for Coriolis past 1200 yards or so.
11.) Consider that updrafts are an unknown variable that can change throughout the day and wreak havoc on your numbers - like 1-2 MOA vertical past 1000 yards - especially if you are shooting over some kind of hollow.

Consider also how often and how far your POI is from POA during a usual shooting session. Oftentimes, this varies between groups and sessions because of parallax and cheek weld issues or other variables. If you shoot 1/2 MOA groups consistently (the exact percentage of true 1/2 MOA groups we shoot with what we call our "1/2 MOA gun" is a topic for a whole other post) but your POI changes by 1/2 MOA so that one group it's 1/2 MOA high and one group it's 1/2 MOA left - well that's not a 1/2 MOA gun even if your groups are 1/2 MOA center to center. It's the center to center 1/2 MOA PLUS the variability in your POI/POA correspondence, so it's a 1 MOA gun. Now if you shoot at 100 and you're zero'd but at 1000 your POI/POA correspondence is off by 1/2 MOA, that's about 5" you have to explain with other variables if you're ignoring POI/POA correspondence and consistency. All of these little things add up, and we make all sorts of assumptions about how consistent everything is, but it's not.

 

[_Windrider_]

You wrote:
Shooting Prime 130g 6.5 Creedmoor @2850
Kestrel Results vs. Acutal
200 yd - 1.5 moa lowered to .75
400yd - 6.25 lowered to 5
600yd - 12 lowered to 11
800yd - 18 lowered to 17.25
1000yd - 26.5 perfect
1200yd - 36.5 held at 38.5

I don't care what "DOC" said. He shouldn't argue the basics nor would his boss. More over, your not understanding what he said. DSF (is a trans curve bender) you still need to do the basics BEFORE going on to DSF etc. or drastically fucking your BC as most are very close from the factory. Further, more CDM's can't use them if your MV is off..

BC has very little effect (repeated at short range) 2850 @ 200y you had .75 MOA difference -- lets look at BC alone and what it would take to adjust that bc for .75MOA @200.. this is only to help you see how little BC effects short range velocity and why you don't want to screw with it until 1-6 bellow are completed. I'll use an horrible G1 .3 BC to get 1.7MOA scope adjustment over my 100y zero, I have to go to a 375CT type solid to get a .9 G2 BC and even then can I get a only .07 MOA advantage @ 3X the BC. So my guess is your ranges are jacked, you MV close but also not exact

repeating:
The assumption is that you can shoot and your ammo is good.
1. you need to know your exact sight over bore
2. you need to know your zero (whatever is) distance is correct.
3. you need to either adjust your scope perfectly to that known zero distance OR create a zero offset.
4. you need to know your exact distance with a tape (not a range finder) to do a Tall Target test. Sorry but that is how it is.
5.you need to create a scope scale based on the TTT.
6. you need to drop confirm MV at shorter ranges as stated-- thats the speed, not changing the BC or drag curve.. Distance and group offsets are what is key here..
^ All needs to be measure not guessed.

These are the basic building blocks needed for any calculator. Assuming 1-5 are dead on.. your 2850 and or Range is just wrong PERIOD, or you missed another detail hidden in 1-5 (my guess is you actual have errors in both). What your seeing BTW is classic.. or you can keep doing the what your doing.. maybe get a BDC reticle and call it a day if you don't want to do the needed work.

Just for clarification, I was just making up numbers to illustrate my questions. I wasn't giving my real drop data. But I do appreciate the explanation.

 

[secondofangle2]

Shooting long range is hard. Fun, but hard.

Too often, a guy like me (back in 2004) goes and buys a gun and takes a class or reads an article and thinks, I'll go start banging steel or woodchucks or deer or whatever at 1000+ yards.

It takes good equipment, lots of practice and experience to get even halfway good at it.

I'm still trying to get to halfway, 13 years after that Rem 700 PSS

 

[_Windrider_]

gotcha - BTW I was not trying to bust your chops ~

It's all good man. Takes a lot more than that to ruffle my feathers. Cheers.