Problem with calcs for 4dof and strelok

[jdavistx]

As you state well if you are working with mixed measurement systems, you have to adjust by a conversation factor since the measurement systems are different. 10 clicks/mrad in a mrad mechanical scope equals 3.6" @ 100 yds. 10 clicks in a MOA system with 4 clicks/MOA = 2.6." Therefore, you fix the number of clicks to see if the scale gives you the desired result.

I'm simply suggesting that the problem would present itself visually due to the different scale factors thus confirming you need to change caps (or not) before you have to make a change, because they would not line up with the expected marking on the label.

It's no different then measuring meters with a yard stick. You can see one is shorter than the other and need a conversion factor (39"/36" = 1.083).

 

[lowlevelops]

I don't know if I've ever seen a barometer that goes below 28. It would have to be more like 2 to make a difference like this anyways. The current official barometric pressure at my home is 29.5 at 2200 feet.

The lower value is actual pressure at your elevation, the higher number is corrected to sea level. Pressure drops roughly an inch per 1000' of elevation, there's a formula if you need to get exact but the 1"drop/1000' elevation rise is a good guess.

 

[jdavistx]

Are you sure you are set for barometric pressure or possibly station pressure

Good question. There seems to be an issue with understanding the difference between Barometric pressure and Station pressure in this thread. There are plenty of articles on the subject and one was just recommended here earlier. I use a Kestrel for shooting (station pressure). It only matches Barometric pressure at sea level as it should. Several inHg off at altitude. It's a factor in calculating air density along with altitude, temp and humidity. Need to know which you are dealing with.

 

[338 dude]

Weather stations report barometric pressure corrected to sea level, which I have never understood. But 4100 feet doesn't make that much of a difference; my house in CO is at 8750 and the difference at 720 yards is 3/4 to 1 MOA.

Also, there is no way a 300 WM requires only 12 MOA at 900 yards.

21 minutes for me could it possibly be dyslexic LOL

 

[milo-2]

If you're dialing 12.35 "MOA" for hits at 905 yards, that is 49.4 clicks. Try switching your 4DOF app into mils and see what it tells you to come up, see if it tells you to come up 4.9 or 5.0 mils.

 

[kmansour111]

Well I have a odd one for everyone. I have been trying to do some long range shooting using the hornaday 4dof and strelok apps. They have both consistently been way off for my gun. See details below. Any help is appreciated.

4dof says come up 17.93 moa and 0.48 left. Actual hits at 12.35 up and 1.25 left.
Range: 12" steel. 905 yards at 8 degrees down. 0 wind. 68% humidity. 55 degrees. Elevation 4100. Pressure 28.5

Rifle: Savage 10t-sr 300win mag.
26" barrel with 1/10 twist.
178 gr eld-x hornaday 3025fps
Zeroed at 200 yards .3 moa hits constantly

I tried it at 675 yards too. It said to some up 8 moa. Actual hits at 5.25 moa.

This really puzzling. I tried to simulate your condition via Strelok Pro - I used 26'' for pressure - with my 26'' 300 Win Mag Sendero zeroed at 200 yards - best I could do is 19 MOA. Last thing I suspect is could the angle (I put in -8 degrees) or distance between the center of scope to center of barrel (mine is at 1.8")

 

[JAYgs8163]

I find it interesting that people don't read a thread in most of it's entirety. That's a entirely different thread though.

 

[Buttermilk]

I haven't read the whole thread but I suspect it's an MOA vs MIL issue.
Either the input in the app is incorrect or the turrets are incorrect as already stated.

 

[Steve gavette]

I haven't read the whole thread but I suspect it's an MOA vs MIL issue.
Either the input in the app is incorrect or the turrets are incorrect as already stated.

Disregard the app. He is dialing in +12 for a 900 yd shot with a 178 gr .30. No way is that right.

 

[Roamingdoc83]

So the OP seems to have, well, where'd he go? Was it (did he call Vortex) the scope/dials? Or... like reading a book with the last pages missing! ;^) Scope is my bet.

 

[JAYgs8163]

^^^^^^ he said he was going to the range this afternoon. If that's anything like my trip it's 3 hours there and back assuming I get past the microbrewery on the way home!!!

 

[jdavistx]

I emailed Vortex. This was their response:

"I would not expect that type of mistake to have happened, however if you wanted to check it out you could run a tracking test on the scope at 100 yards. If you zero the scope then dial up 10 MOA it should hit 10.5 inches above the zero (provided you are at exactly 100 yards). If it was MRAD it would hit 14.4 inches above the zero. By running the tracking test at 100 yards it will remove all of the variables of the ballistic calculator and determine if the scope is working properly.

That being said, it would be very unlikely for that to happen and it would be far more likely that there is an incorrect input in the calculator that would be causing the issue. Things like muzzle velocity, scope height, ballistic coefficient and environmental factors all will have an impact on the ballistics at that distance."

.... just reporting the news.

 

[SammySTW]

Nice quick response from Vortex customer service!

 

[BK6x47L]

The tracking test will tell the tale. I cannot think of any input variables that would account for the error. I do agree that getting wrong turrets on an Mrad scope is unlikely, but that is the only thing that completely explains the error,....AND also gives the exact amount of clicks/dope to provide for the hits that he is getting on target.