I need some help troubleshooting a ballistic calculator. I'm running Strelok and I can't get the trajectory to match actual trajectory.

7mm WSM - 1:8 twist
Berger 180 vld hunting
R22
Federal 210 primers

**I haven't chronographed this load yet, but have all of my other inputs correct in the app.** The only change I make is MV to attempt to get the table to match the actual impact of the bullet. I can get them to be the same at specified distances, BUT when I step out to the next distance it's off. My trajectories don't match between the app and the actual shot. Grouping is fine, just elevation is off.

For example, I dial 3.6mils for 750 yards and shoot a few times. Grouping is decent. I mess with the MV in the app to where 3.6mils shows for the 750 yard shot. With the correct MV at 750 yards, my table shows below:
100 - 0
250 - 0.5
500 - 1.9
750 - 3.6
1000 - 5.8

Actual elevation shots:
100 - 0 mils
250 - 0.8 mils
500 - 2.2 mils
750 - 3.6 mils
1000 - 6.1 mils

I can change the speeds in the app to gain the correct elevation at each one of these distances, but then the rest of the distances are off....what gives?? I'm stumped.

I'm still pretty new to this long range shooting, but I have a pretty good idea of the different inputs I need (altitude, BP, Bullet weight, BC, MV, etc). I'm just trying to get the trajectories to match if possible.

Any ideas? Did I input something completely out of whack or what?

**Disclaimer, I did chrony the first set of loads I made up at .5gr increments, so I wasn't just slinging lead downrange completely blind. I picked a MV between two of the .5gr increments that were closest to this load.

It probably won't make you feel better, but I'm having the same issues. Here's my 6.5CM table (from Strelok+) with actual results.

So I'm shooting a 140gr amax (BC .585) at 2685 fps, and my rifle is zeroed at 100 yards. Strelok is telling me that I should be dialing these values at certain ranges:

200- .5 mil
300- 1.3 mil
400- 2.1 mil
500- 3.0 mil

I was making very reliable groupings at each range using these values, however:

200- .4 mil
300- .9 mil
400- 1.5 mil
500- 2.5 mil

I've tried fiddling with every variable, finding ballistic calculators where I can input the G7 BC instead of G1, and I just can't get it to line up. I'll be watching this thread to see what sort of input you get. Only explanation I can come to is that my scope isn't tracking correctly. What sort of scope are you using?

Get your MV in the program to match the DOPE for the four that it can match.

The error at 750 yards (ONLY!) is tracking error in the scope. There is no scope that tracks 100% perfect. If the rifle/load/scope shoot the same DOPE every time, you're OK.

Just know about that error, at that point in the turret, for future elevation corrections the program gives you, for different environments.

Put the BC back to where it was, and adjust MV until the calculator matches known DOPE.

NF ATACR f1 5-25x56. I've already done a tracking test with it at 100 yards and it did fine.

I see yours is off as well, but when I was out shooting (its been a couple of months now at that long range), I would get at least one of the distances lined up between actual shooting and Strelok. I was pretty consistant at 750 in elevation, so I changed MV on Strelok to where it was at 3.6 mils (actual shooting was 3.6 also) but then none of my other numbers in my table matched the actual shooting. I'm stumped.

Would that be magnified more at, lets say, higher elevations?

No.

If it's got a .3 Mil error at a DA of 1000', it should hold a .3 Mil error at 3000', 6,000' ect.

Awesome. Thanks. That puts this into a better perspective to understand. BTW one of these days I can break away on a free weekend, I'll be coming to see you for your class.

The closest I can get to matching the dope is if my MV is 2850 fps. Isn't that a little extreme, especially with the relatively mild loading of 41.7gr H4350?

And I chrono'd my loads right before going out to the long range, so I'm not sure what could have happened there. I had an ES of 11 fps, average of 2685. Could the chrono just be that wrong?

I trust DOPE more than a chronograph, especially an optical chronograph. Is yours an optical?

I have put no less than 4000 140 gr A-maxes down range. Using a G-1 of .585 and an MV of 2800 fps my DOPE is:

200 .4
300 1.0
400 1.8
500 2.6
600 3.6
700 4.5 to 4.7 depending on DA
800 5.6 to 5.8 depending on DA.

I'm doing that with a 25" barrel and 42.8 gr of H-4350. Previous load on a former lot of powder was 42.4 gr H-4350, so lot to lot does vary. Yours just may simply be making more speed with less powder.

Looks like you've got this figured out, already.

Ehhh I don't know if I would say that lol. It's all been kind of self taught with a little help from an extended family member.

Have you guys corrected the pre set weather/altitude settings in the app? I had used the Pro version for a while ( not the free one )and it allowed me to make corrections within the app by changing the elevation input. Then it would calculate my estimated MV

FWIW I've had more 1st round hits at distance since using a kestrel with applied ballistics. Not saying it's a necessity but it definitely makes life a tad easier

I use "Shooter" ballistics on the phone. But when these thing happen with that app, that's what I do to correct it.

I started with the free version, but upgraded to the next one. Cant really remember why though. But yes, I do manually plug in the weather and altitude based on where I am at the time.

Use the target trajectory icon to plug it your corrections and disregard the calculated mv. If all your inputs are correct you should be good to go

If you are running a G1 BC, throw out your calculated data. Run a G7 BC, and it will firm up your numbers. The G1 BC is velocity dependent, and rears its ugly head once you start to shoot further out. As velocity slows down, the actual BC drops. When you run your program, you probably only enter one value for the G1 BC, which is probably .671. See below.

The G1 BC of the 180 grain VLD is, per Litz data

.720 above 3000 fps
.690 from 2500-3000 fps
.676 from 2000-2500 fps
.653 from 1500-2000 fps
.632 below 1500 to 1100 fps

The G1 BC is listed average of .671. Looking at the Litz data on the actual G1 BC, you can see the actual G1 BC is dropping as the bullet slows. In most all ballistic programs, you enter one G1 BC, and it calculates that one BC for the entire flight path at the higher velocity number. If you use a G1 BC, you have to enter in each velocity range BC for it to work correctly. When you run this data incorrectly, the G1 BC will ALWAYS have less drop than actual filed results show, because the average G1 BC is used for only one velocity at the higher end. But the bullet is slowing down in flight, and therefore the actual G1 BC is reduced, which most programs do not account for.

ALWAYS run the G7!!!!!!!!!!!!!!! The G7 drag function is for a BTHP bullet. The old style G1 BC is for a lead soft point flat base bullet.

So my question is (which I probably already know the answer), which BC are you using to calculate your drop in your app?

I almost wonder if I mismeasured scope height? I'm going to get this thing figured out one way or another, but will probably be the next time I get a chance to shoot long again.

I tried to use the trajectory calibration, but only allows me 1 distance and 1 elevation input. I wish I could plug in each number I have to calculate a "custom" trajectory.

It's definitely the G1 that is programmed in. So I should run the G7 - 0.345 for the bc? it doesn't specify in my app G1 vs G7.

Exactly!! This is the issue. You need to run the G7 BC of .345, and problem solved!

Your app will have an option to use a G1 or G7 BC. Use the G7 BC and use .345. Then chronograph your ammo to know exactly how fast it's going to help firm up your numbers. If you have no chrono, then use your field data to calculate your speed.

Also, R22 is a temp sensitive powder, and will run slower speeds in cooler weather and faster speeds in warmer weather. If you chrono'd in cooler weather, and are shooting in hot weather, the dope will not line up either.

I didn't think about that. I have been noticing the slightest pressure signs while shooting in extreme heat though. Zero weather was 59 degrees (app has input for zeroing weather: temp, BP, & alt.) and when I shot, it was 87 and I plugged in the alt and BP.

With what you said, any good temp stable powders I should try? After deer season (and the rest of the bullets I have loaded are gone) I'll be switching to the Fed GM210M primers. I out of the regular Fed 210 and finally found some 210M in stock and picked a couple up.. I figured since I'm going with different primers, I'll have to do some load testing again. Might as well try a different powder.

Yes. A lot of shooters run into this problem when the summer time temps heat up.

First, is your rifle a short action or long action? If it's built on a short action and feeding from the magazine, you are limited to about 8.860 to 8.880" max length. If you are running on a long action, you can seat the bullet out further and increase your case capacity. The powder recommendation depends on your set up. Also, what is your COAL now with the 180 VLD-H? Alsom I'd recommend a magnum primer, like the Fed 215. A 210 will do, but it's a little light.