Magnetospeed vs Calculated MV

[Bigwheels]

Scope height is 2.3"
The ranges with dope:
908yd. 27.96"hg 41*F 73%RH +2* Incline
20.25 moa. Light mirage & wind.
1416yd. 28.09"hg 41*F 78%RH -6*Incline
42.25moa. No mirage or wind.
1713yd. 28.0hg 46*F 47%RH -6*Incline
60.25moa. Heavy mirage & switching wind at this range.
Data generated with my Kestrel & Kilo2400.

 

[Deleted member 113831]

Scope height is 2.3"
The ranges with dope:
908yd. 27.96"hg 41*F 73%RH +2* Incline
20.25 moa. Light mirage & wind.
1416yd. 28.09"hg 41*F 78%RH -6*Incline
42.25moa. No mirage or wind.
1713yd. 28.0hg 46*F 47%RH -6*Incline
60.25moa. Heavy mirage & switching wind at this range.
Data generated with my Kestrel & Kilo2400.

I played with the numbers. If I giave the bullet an 8 percent increase in bc to .405 G7 and bumped velocity to 2860fps then the numbers are within .25 moa at all ranges.

I think you may have a couple of different things going on. An increased bc due to a faster twist and a slower than actual mv reading. Anyway, like I said, with the numbers I gave it is within .25 moa to 1713 yds.

 

[Bigwheels]

Hey thanks! I'm using AB with the Custom Drag model & I think I can only use the internal truing function, and that brought my MV to 2872 and +1.7%@Mach 1.1 this has it about the same as what you found.
My primary is FFS though and it will only accept a G1. I haven't sat down and trued it up yet though so very soon...
Then I also have Trasol, and 4DOF. Was trying to get the 4DOF to work with my numbers but it is a PITA to calibrate. Also doesn't have a scope calibration input so I'm probably screwed trying to use that unless I want to take what it gives and then adjust the output for my scope offset/click. I'll run through FFS here this afternoon and see what I come up with.

 

[Deleted member 113831]

Hey thanks! I'm using AB with the Custom Drag model & I think I can only use the internal truing function, and that brought my MV to 2872 and +1.7%@Mach 1.1 this has it about the same as what you found.
My primary is FFS though and it will only accept a G1. I haven't sat down and trued it up yet though so very soon...
Then I also have Trasol, and 4DOF. Was trying to get the 4DOF to work with my numbers but it is a PITA to calibrate. Also doesn't have a scope calibration input so I'm probably screwed trying to use that unless I want to take what it gives and then adjust the output for my scope offset/click. I'll run through FFS here this afternoon and see what I come up with.

I also ran the numbers in Strelok Pro. If you use the old bc of .368 G7 that Berger was listing for that bullet, then 2850fps will put you within .5 moa at all ranges.

 

[Bigwheels]

I use Streloc Pro only for my hunting rifle since it has the reticle I use loaded in it. Never been able to true that one with the ELR rig well enough to suit me.
I just ran a bunch of numbers through FFS and decided on MV-2860, BC .800 and its really close. May be impacting low at 1713yds but the mirage was so heavy when I shot that I can't be sure where the TGT really was anyway. Hopefully I'll be able to have another day when the wind is at least steady, and cloudy so I can check this out again. Also want to check it out at around 2100-2200 yds and plug those numbers into AB to see what it does.

 

[Bigwheels]

Update.
I had another perfect morning to shoot again so I set up at the exact same spot for another go @ 1713yd. I ran my buddies Magnetospeed & at the same time shot across my old Shooting Chrony.
Well with a 0 wind hold I fired 10 rnds which included my CCB shot. Both chronographs showed all following shots to be in the 2830's. However AB was right on after last time truing with 6 consecutive hits on tgt. But it corrected my MV to 2873fps.
Conditions were:
Temp 39*
Press 27.69"
RH 88%
1713yd at -5* declination
Very light winds of 1-2mph from 270*
60.5moa hit about shoulder high from center. 60.25moa hit in a line about belly button high. Not sure why the large change but I've seen it many times before.

 

[Bigwheels]

Here's a pic of the spot.

 

[Deleted member 113831]

Great job Jeff! I hope to get mine out in the next couple of days.

 

[Bigwheels]

Thanks. I was going to invite you but I didn't want to waste your time if the fog didn't clear off. But it did. Had to wait for about 30 min after getting set up.
Don't know why the scope pic washed out so bad, not that bad at all on my phone... But I was set at about 40X on the spotter, and zoomed in with the camera too.

 

[Deleted member 113831]

Thanks. I was going to invite you but I didn't want to waste your time if the fog didn't clear off. But it did. Had to wait for about 30 min after getting set up.
Don't know why the scope pic washed out so bad, not that bad at all on my phone... But I was set at about 40X on the spotter, and zoomed in with the camera too.

I was working today anyway, but if we get nice weather and you are going, I could find a reason to be sick.

 

[Bigwheels]

A possibility. Starting a new job tomorrow so I'm not going to be able to shoot on weekdays anymore. I'll be watching the forecast for next weekend.

 

[jmarch68]

Ya, I wasn't saying you don't.. But some of the feedback on here obviously didn't. I was not even really addressing your issues, sorry..

In your specific example, you have no way on confirming whats actually going on.. did the position you build have you drive the gun slightly differently (lighter dive can cause higher impacts) .. is the MV off just a hair.. is the range finder perfect etc.. I mean a tiny 1% ranging error at 1700 make more than a minute of difference in perfect conditions. A switching 270/90 10mph wind is a minute.. Mirage will generally have you aim high..

If your within 1 min at that distance your distance with off angle shooting etc.. I think that's really good, your second shoot should be money

Now if your high, then low, then high.. it is almost always a slight range error

Tag

 

[Bull81]

Update.
I had another perfect morning to shoot again so I set up at the exact same spot for another go @ 1713yd. I ran my buddies Magnetospeed & at the same time shot across my old Shooting Chrony.
Well with a 0 wind hold I fired 10 rnds which included my CCB shot. Both chronographs showed all following shots to be in the 2830's. However AB was right on after last time truing with 6 consecutive hits on tgt. But it corrected my MV to 2873fps.
Conditions were:
Temp 39*
Press 27.69"
RH 88%
1713yd at -5* declination
Very light winds of 1-2mph from 270*
60.5moa hit about shoulder high from center. 60.25moa hit in a line about belly button high. Not sure why the large change but I've seen it many times before. View attachment 6894584

I have this same problem with AB using the Custom Curves and the 140 RDF’s. In order to get the predictions to match actual AB increase my velocity almost 50 fps. I contacted AB and was told something was wrong with my data or rifle. When I brought this up on another forum they said they’d look into it. The custom curve worked perfectly on a 80 VLD and my 223 out to 1168 yards so I think it’s bullet specific and AB has the drag model wrong on certain bullets. The 140 RDF’s for example in AB’s library is listed with a .313 G7 BC, but I have found the .330 BC listed by Nosler to be very accurate and actually needed to increase it slightly in truing.

 

[Bigwheels]

That's good info. I hope that they do look into it. I had the same thing going on with the 230gr Berger too but pretty much stopped shooting them in favor of the 225ELD. At the end of the day I don't really care what numbers are in there as long as I get accurate results out of it. I have FFS very close now also but I had to adjust the BC, MV, & DK to get there. I'm not a big fan of AB but right now it's the only one that matches my observations in the field. And I used the truing function alone to do it. Obviously the MV isn't 2873fps but it's matching my observations. But I would prefer to have all the inputs to match my observations as well. I looked at shooting another truing round at even longer range but until they do some more logging I can't get anything closer than 2575yds. That's an absurd range for my little 300Win Mag since I don't have one of those prisms to mount on my scope. If anyone has one I could bum for a few I'm game...

 

[Bull81]

That's good info. I hope that they do look into it. I had the same thing going on with the 230gr Berger too but pretty much stopped shooting them in favor of the 225ELD. At the end of the day I don't really care what numbers are in there as long as I get accurate results out of it. I have FFS very close now also but I had to adjust the BC, MV, & DK to get there. I'm not a big fan of AB but right now it's the only one that matches my observations in the field. And I used the truing function alone to do it. Obviously the MV isn't 2873fps but it's matching my observations. But I would prefer to have all the inputs to match my observations as well. I looked at shooting another truing round at even longer range but until they do some more logging I can't get anything closer than 2575yds. That's an absurd range for my little 300Win Mag since I don't have one of those prisms to mount on my scope. If anyone has one I could bum for a few I'm game...

It worked for me from 1000 out to 1682 yards with my 6.5x47 but what concerned me was if the MV had to be increased that much it could throw it off at other ranges under different conditions. I hope they do what they say and look into updating the drag models and correct these issues. I would love to have FFP and have almost pulled the trigger on it several times, I always talk myself out of spending that much on the software and unit to run it though.

 

[Bigwheels]

I hear ya. I bought FFS many years ago and am still running their version DeltaIII. They're up to version Delta VI now I think and they have added a lot of stuff but I still haven't paid for the upgrade. This is still working but I have to do all the truing myself. Gives me a ton of info doing it rather than letting it all get done in the background.
Now so far AB is giving me the correct DOPE at 1700, 1400, and 900 so I think I'll be GTG. I just wish I could have found a spot there that would have given me 2000-2100 yd but the trees, and lay of the land didn't cooperate.
I still have the other spot when the snow melts that I can get there and its a couple thousand feet higher up so I can see how it does when the conditions change. Then if it works well here I'll take it over the mountains to another spot where I can shoot these ranges at 7000'asl. Only then will I know if it's really ON.

 

[Deleted member 113831]

Jeff, did you ever shoot this at 500 to true your velocity first? I would be interested to see how that lines up with your magnetospeed data and other drop data.

I got mine out to the mountain yesterday and was only able to zero at 100 and true velocity at 500. Both AB and Strelok are saying 3157 fps w/ 300 Berger OTM. I hope to get it out to 1200 and 2000 next week.

 

[Bigwheels]

I haven't since the barrel stabilized. I did at first but I then discovered that the MV was still increasing. I don't think it changed much but I do plan on checking my short range DOPE to verify next time out.

 

[Sogan]

Interested in how your 500y shots and MV match up

 

[CharlieNC]

I know you're concerned about a consistent 1moa bias. In general I'm amazed the ballistics work as well as they do using a bc to represent a specific bullet vs a different projectile from which the calcs were trued. Being able to true within an app after a few range sessions and subsequently compensate across varied enviornmentals resolves any concerns I briefly held concerning trueing vs the measured velocity. But if you have a consistent 1moa bias at all distances beyond 100yd zero, something else is off.

 

[Bigwheels]

I don't have a consistent 1moa bias. What I have is a MV measured by 3 separate chronographs 2 of which were used simultaneously over 2 strings of 10 shots. All three gave similar readings of 2825fps +/- a few fps & 5 different ballistics engines that true the velocity up to the 2860's + to get results within 1/2-1moa of observations in the field under near perfect conditions. Then when trued @ 1K-1500 then results trend back down beyond that to a mile.
This using "dopler verified" BCs.
So in a nutshell I must increase the MV in the software 50fps or more for 1K-1500yds then adjust back down beyond that. I won't be surprised if another adjustment @ 500yds is required.
With all my software if I use my measured velocity I must bring the BC well into the .800s G1 or .400s G7 to get the observed DOPE. Then it's off again at longer ranges.