DOPE Help please

[mram10]

My friend and I built a 30 STW with 28" 1:10 twist. Load it loves was 87-89gr RL33 with 215(.696bc) and Fed215s. I went with 87gr to keep brass life longer. His Ohler said we were getting 2995-3015fps, but when I put all the info into my shooter program, zeroed at 300, the values are not correct. Here is an example of REAL vs program values:
600 6.0 vs 7.0
800 11.25 vs 12.7
1000 18 vs 19.2

The values on the left are actual target moa v program. What is going on?

Other values:
Spin drift checked, Twist 1:10, Bullet length 1.6, Stab Factor 1.59
Coriolis effect checked, Lat 43deg, Azimuth 150
Shot off bipod and rear bag(walnut shells). Groups <1moa to 1000, <.5moa vertical

 

[CJ6]

BC variance (distance) or Chrono (did you adjust chrono vel. back to the muzzle). Get a muzzle velocity then set the chrono up @ 100 yds (get another velocity) see how that compares to your programmed settings. Make sure ALL the atmospheric data is included also.

 

[JohnKielly]

What ballistic program are you using? Does it allow for scope height?

Try to run the figures over http://www.jbmballistics.com/ballistics/calculators/calculators.shtml and compare.

Cheers, John

 

[FatBoy]

Box test your scope. Your adjustments may not be exact, and may just vary in some spots along the adjustment range. I have had this a couple times.

 

[mram10]

The chrono was about 15 ft in front of the rifle. The program is Shooter. The environment is all in correctly (baro, temp, humidity, elev, etc). I will check the clicks. It is a mark 4

 

[Dusty Stevens]

Damn i thought this was about something else. Sorry bout that.

 

[Bryan Litz Ballistics]

looks like your scope zero is 1.25 MOA out. I suggest you re-verify your zero. If you adjust your zero by 1.25 MOA, then all predictions are within 1/4 MOA.

-Bryan

 

[mram10]

Zero is right on. I shot at 300 and hit center. All these shots are on paper and distances taken with different rangefinders to verify. This is not making sense.

We start at 300, go to 600, 800 and 1000, then return to 300 since it is the crutch of the chart.

 

[Paul Milone]

I've had similar issues. I've checked with all sorts of people. Most say that "Bullets do what they do". If your shooting groups, don't worry about it. Remember that BC is only a theory.

 

[SheepDog]

The software does the best it can to make predictions. A DOPE chart lists the actual adjustments you had to make to keep the group on target at different ranges and under different conditions. Your targets are right, your software is off.

 

[rcparker1]

Are you shooting true horizontal. I've seen people shooting up or down hill and have errors they didn't compensate for

 

[DOGCAPPER]

Looks like calculations vs real world.
Your variations are less than you will have from session to session of shooting. Just click the scope and shoot.

 

[mram10]

Late to the party, but to fix the issue I input a 1.6” high at 300yds to make the dope correct out to 1000

 

[Depart123]

Did you zero and then shoot at distance under the same light conditions?

 

[mram10]

Zeroed at 300 and shot to distance within an hour of each other

 

[boltfluter]

I would definitely do a tall target test to confirm that your click vales are truelly. 25 MOA. Or whatever they are suppose to be. Also, make sure your scope height above the bore is correct. Good luck and keep us informed.

Paul

www.proprecisionrifles.com

 

[moondog]

Funny, I bought a Kestrel 5700 and get the opposite results. Shooter and JBM are pretty much spot on with 4 different rifles. Kestrel ballistics are
way off. Just use the kestrel for environment data now.

 

[4xforfun]

Are you shooting true horizontal. I've seen people shooting up or down hill and have errors they didn't compensate for

The difference between a 0 degree and 10 degree incline in elevation change at 1000 yards only changes impact by .5 moa. You can't "not realize" a 10 degree incline. Maybe 1 or 2 degrees slope could be missed, but that wouldn't affect impacts. To get the 1.2 MOA difference that the OP says he is off at 1000 you would need an 18 degree slope. That, my friend is a big slope.

This according to my Shooter app.

Tod