Range Report Trueing data...need help

[Vandy321]

This probably belongs under stupid marksmanship questions...but can MV have a 100fps swing with 30 degree temp change? Is there any rough gouge for that? Cannot find what the of powder hornady uses, but shooting factory 147 eld-m if that helps.

Had no chrono for my zero day...I went out to verify drop at 620....had a .4 mil discrepancy which is outside the adjustments for form factor on Hornady app. I get the same result in AB as well. Tell me to check my data (not having a MV at zero makes it tough)

Looking for any inputs/suggestions

6.5 PRC 26" 1:8
Zero day was 63 deg and 60% humidity
Today was 90 degrees 15% humidity, chrono'd at 3085, so I threw 3085 in and was .4 low at 620. Truth data was 3.0 mil at 620, 2.9 mil at 600.

The data lines up if I throw in 2985 for my zero day MV...is 100fps a realistic swing with a 30 degree temp increase? Still having to use a 1.09 form factor with that.

 

[JustSendit]

This probably belongs under stupid marksmanship questions...but can MV have a 100fps swing with 30 degree temp change? Is there any rough gouge for that? Cannot find what the of powder hornady uses, but shooting factory 147 eld-m if that helps.

Had no chrono for my zero day...I went out to verify drop at 620....had a .4 mil discrepancy which is outside the adjustments for form factor on Hornady app. I get the same result in AB as well. Tell me to check my data (not having a MV at zero makes it tough)

Looking for any inputs/suggestions

6.5 PRC 26" 1:8
Zero day was 63 deg and 60% humidity
Today was 90 degrees 15% humidity, chrono'd at 3085, so I threw 3085 in and was .4 low at 620. Truth data was 3.0 mil at 620, 2.9 mil at 600.

The data lines up if I throw in 2985 for my zero day MV...is 100fps a realistic swing with a 30 degree temp increase? Still having to use a 1.09 form factor with that.

Intuitively, I find it unlikely that box 147gr ELDM would have a shift of ~100fps, at just +/-30 degrees. You might rule out a few other culprits if you did not already. Confirm zero, confirm scope tracking, check MV with chrono again, take a look at the data in the solver, ensure something is not incorrectly input. If everything checks out, true again and record the results.

There's a lot of other factors involved, my suspension is it's not the powder being sensitive.

 

[Vandy321]

New glass, have not dont a tall target testwith this glass yet, but haven't seen the LRTS posted on here with any issues they all seem to track well

Zero was done yesterday. Nothing changed, dropped or anything else except temp. Wish I'd had a chrono yesterday.

Checked data in AB, hornady 4dof and JBM, it's all input correctly...I input today's MV at 90 degrees and was way low at 600

Should I take out the zero height offset? I calculated that off the range buddy app at .14" high at 100...are people using zero offset?

 

[JustSendit]

New glass, have not dont a tall target testwith this glass yet, but haven't seen the LRTS posted on here with any issues they all seem to track well

Zero was done yesterday. Nothing changed, dropped or anything else except temp. Wish I'd had a chrono yesterday.

Checked data in AB, hornady 4dof and JBM, it's all input correctly...I input today's MV at 90 degrees and was way low at 600

Should I take out the zero height offset? I calculated that off the range buddy app at .14" high at 100...are people using zero offset?

There's a few reason to use the zero offset, it can be used with turret clicks that do not allow the point of impact to be at the point of aim. An example is .5MOA elevation adjustments move the zero outside of the 1in target. Now the solver calculates that difference in the hold. Typically, with .1mrad adjustments, it's not necessary.

Another reason to use the zero offset is to have a different distance zero, or if between different bullets you had a shift and did not want to slip the scales.. there's a few reasons why it is there. But I would be careful why I use it.

Try taking your zero offset out of the solver, and see what the hold is without. How did that line up? Was your zero high?

 

[seansmd]

If reading this correctly you didn't have a Chrono where did you get the MV to enter into the app for the 600y elevation? If this was from the box then 100fps difference is fine.

You don't need mv for a zero, you need confirmed distance (100y is best), site over bore, and twist rate. With these three variables and the ammo, your zero is your zero.

 

[Vandy321]

Zero is not in question, but did not have a chrono on that day. Had a chrono available today, 30 degrees hotter humidity down 45% , chrono'd at 3085...threw that in the solver and bam, .6 low at 620...fine tuned data and re-measured height above bore, came up to 3.0 up and put 4 rounds on...solver saying 2.7 up

Zero group POI of 3 shots touching was .22" low at 100...so I dialed up another .1 before I set my turrets, my math for dummys say that's .14" high now...even if I take that out and set it to zero...I still get correct data with an MV set to 2985 into my zero data...real work MV today was 3085

 

[JustSendit]

Zero is not in question, but did not have a chrono on that day. Had a chrono available today, 30 degrees hotter humidity down 45% , chrono'd at 3085...threw that in the solver and bam, .6 low at 620...fine tuned data and re-measured height above bore, came up to 3.0 up and put 4 rounds on...solver saying 2.7 up

Zero group POI of 3 shots touching was .22" low at 100...so I dialed up another .1 before I set my turrets, my math for dummys say that's .14" high now...even if I take that out and set it to zero...I still get correct data with an MV set to 2985 into my zero data...real work MV today was 3085

Math sounds good to me .36" per .1mrad at 100yds.

You chrono'd at 3085, and hit .6 low at 620? So to hit with a 147eldm at 620yds, you held a 2.4mil? I would say something is off. For a dalt of 2750, 90temp, SP29.5, lat 35, DOF 0:
MV 2985: 3.15mil
MV 3085: 2.92mil

At 620yds the disparity between the two isn't that .4mil.

 

[Vandy321]

I guess the best answer is to zero again and get a powder temp and MV with that zero data, so real world numbers are going into the

Math sounds good to me .36" per .1mrad at 100yds.

You chrono'd at 3085, and hit .6 low at 620? So to hit with a 147eldm at 620yds, you held a 2.4mil? I would say something is off. For a dalt of 2750, 90temp, SP29.5, lat 35, DOF 0:
MV 2985: 3.15mil
MV 3085: 2.92mil

At 620yds the disparity between the two isn't that .4mil.

Dialed 2.5 up initially I think with 3085 input as Mv...real world was 3.0 today.

DA was 8 or 9k, shooting at 5500ft or so elev

I should it, I think I had 1.7 in for a scope height initially, after that measured again, 1.875...that moved data from the initial 2.5 up to 2.7 up...still .3 off real world

 

[JustSendit]

I guess the best answer is to zero again and get a powder temp and MV with that zero data, so real world numbers are going into the


Dialed 2.5 up initially I think with 3085 input as Mv...real world was 3.0 today.

DA was 8 or 9k, shooting at 5500ft or so elev

I should it, I think I had 1.7 in for a scope height initially, after that measured again, 1.875...that moved data from the initial 2.5 up to 2.7 up...still .3 off real world

Is 4DOF saying 1.7 to 1.875 is a .2 elevation shift? That's huge, from what I have seen I would expect a .0something shift, .03-.05. Not 2 tenths.

Otherwise, yeah I agree with you, confirm zero, chrono again, and true that MV. Sometimes these things work themselves out by starting back at ground zero to speak.

 

[Vandy321]

.2 and that's including form factor from 1.0 to 1.1

 

[JustSendit]

.2 and that's including form factor from 1.0 to 1.1

Ah, I screwed around with 4DOF for a couple of months, not keen on all the ins and outs like I am with AB.

 

[pell1203]

Per chance did you recently run an update on the Hornady 4DOF app recently?

I had been all squared up with dope out to 1000 meters and a few days ago I went and shot at 550 meters and the app called out for an elevation of just under 3.7 mil. Under nearly identical conditions previous dope had been 3.9 mils.

Sure enough, I tried 3.7 and hit 0.2 mil low. Adjusted to 3.9 and was right on target. Been scratching my head as to why it is suddenly off so far on the low side since rifle was pulled up from favorites without changes.

As far as I can tell, there was an app update that was processed between sessions and I am wondering if there was a database change that occurred behind the scenes to the bullet profile or to the algorithm the app actually uses to arrive at the corrections?

In either case, it is not yielding accurate results any longer.

[Edited to add: Last update was about three weeks ago]

 

[Vandy321]

I'd blame it on the all, but at 3085, ABx Hornady and BallisticsArc are all calling for 2.7 and it takes 2985 or 2980 in all 3 to get to real world 3.0 mil drop.