Thread: Ballistic Calc Help

Hi all - am trying to come up with a LR solution for a new rifle. Distance I've been working at so far is 300m; the theoretical solution is 3.98MOA; actual solution is 3 MOA. Here's the details:

Rifle: Tikka t3x 7mm RM w/ Leupold vx5 3-15 (installed by Manawatu H&F)
Ammo: Hornady 162g SST
Factory MV: 3030 fps
Chrono MV avg: 2995 fps (personal chrono; has been accurate for other solutions)
Impact velocity @ 300m: ~2400 fps (Trentham targets):

Theoretical Solution @ 300m: 3.98MOA



(SST is a boat-tail ammunition but Hornady doesn't have a G7 BC so am using the G1 (https://www.hornady.com/bullets/rifl...-162-gr-sst#!/)

Actual Solution
I had a shoot at Trentham 2 weekends ago and ended up working my way down to a 3.00 MOA adjustment after shooting high and ended up with this:



And then last weekend I shot a small fallow that was sitting down at 315m using a 3MOA adjustment (also slightly uphill shot). Shot was exactly where I expected it.

I've tried fiddling around with MV, BC, Weather, etc inputs to see what bring the solution down from 3.98MOA closer to 3MOA @300m). The only one that gets it even close is adjusting the sight height from 1.5inches (which is accurate) to 3inches (which is not accurate)

I really just need to go out and shoot at 500 or 600m to validate it and hope to do that shortly but am looking for your guy's thoughts before I have a chance to do that.

Any help or thoughts are appreciated.

Up the velocity until your solution is 3 now and then try use that new velocity’s solution at 500 and see if it’s helped?

Check to make sure your sight height is true too. My vx5 in talley xlow lightweights sit at 1.6" on a tikka

Have you checked you are zeroed at 100m?
Another possible factor is your clicks aren’t 0.25moa, one of my scopes works out to 0.28moa.

Good point at Cigar so think that’s common in the Z5

Methodically work through all your inputs and make sure everything is bang on incl your zero. Then adjust MV as much as necessary to produce the correct solution to match your real world results.

You can also do a tracking test to see if your scope dials true MOA or maybe it’s out a bit and dials less like Shooters MOA (1” at 100 instead of 1.047”). You can adjust your scopes dial from TMOA or SMOA in the ballistic calculator to best match and then ultimately adjusting MV will get it doing what you need. Everything else needs to be correct though.

300 isn’t all that far to verify a solution either. Try get out to 500ish if you can or further if you expect to shoot further then that.

A good example as mentioned is my Swaro Z5 dials something like 0.975” which is even less then shooters MOA. Therefor even with my ballistic app set to SMOA I still have to drop MV quite a bit in order to make my solution match up and tell me to dial enough.

Is Trentham range yards or meters, if 300Y not m, then that would easily explain difference

As others have said, measure scope height, double check zero, do a tracking test and measure click values, confirm your zero and target ranges are yards or meters

The saga continues below.

Thanks for all the input.
- To adjust the MV to get to a 3MOA @ 300m would be 3300 fps. I don't think is that's in the realms of possibility, right? Could be but majorly contradicts the factory specs and the chrony readings.
- Have checked the zero a few times and am very confident it's 100m. Will check it again sometime this week out Kaitoke.
- Trentham does both yards and meters but there was a lot of chatter the other week if we were supposed to be shooting yards or meters and it was definitely 300 meters. Shooting the fallow at 315 at the same 3.0MOA adjustment validated that for me.
- Measured thse scope height and is 1.75 inches at most, def not 3inches
- Checked the scope and it is supposed to be .25 MOA adjustments. Might have a go at the test you mentioned SS that'd be interesting.

Today, Trentham were shooting 800y / 900y. That's too far for me and I wasn't even thinking of going but got a bit fed-up trying to figure out the theory so at 1130 said bugger it and decided to go and see if I could get something on the target using the adjusted solution (changed site height to 3inches; which aligns to 3MOA @ 300m).

Solution was 16.75MOA adjustment for 800y (730m) and despite it being a day of strong gusts, some distracted shooting from myself (I never seem to shoot well with others around), and having never shot out that far before, I ended up with the below.



There's not a great waterline but I think the distractions (didn't follow my process ) and the strong and gusty headwind, it's somewhat validated my solution. Granted, won't be trying to shoot a deer at this range as I've obviously got some work to do but I think the MOA adjustment of 16.75 @ 730m is accurate.

Thanks again for all the input. Hoping to have a crack at something a bit closer (~500m) this weekend and will report back.

Several issues here.

Is the zero distance on your app 100 yds or 100m ? The rest of the values look imperial, so I suspect yds.

No way on gods green earth you scope height is 3.0 inches... Measure from the centre of the bore to centre of scope tube, at a point halfway between the rings.

Use a G7 BC, G1 is crap.

Get someone to use the NRANZ labradar to measure your MV.

Use a range finder to measure the ACTUAL distance, do not trust the range label on the mound, or what another person is telling you it is... Make sure the units you use match the units in the app.

Shoot a string of 5 shots over the labradar and let me know what your SD is. A lot of the vertical dispersion may well be due to MV variation.

Heres a screen shot for my inputs in strelok. Matches pretty close at 720m. 730m was less than 2 clicks more elevation.

Some more thoughts...

From memory, and this is going back at least 5 years - the 300m at Seddon is really only used for a couple of weekends in Jan. The rest of the time they use 300 YARDS.

Please ignore the MV on the electronic target. You are wasting your time thinking this is accurate. It is a mathematical calc using an extremely short distance (couple of inches on the microphone stalk), and does not account for the entry angle of the trajectory.

Looking at the Litz / Applied Ballistics book, your 162gr SST has the following BC:

G1 : 0.535
G7 : 0.274

I also see that your zero atmospherics and those for when you are shooting are the same. Did you record actual atmospherics when you zeroed ?

Originally Posted by ebf

Some more thoughts...

From memory, and this is going back at least 5 years - the 300m at Seddon is really only used for a couple of weekends in Jan. The rest of the time they use 300 YARDS.

Please ignore the MV on the electronic target. You are wasting your time thinking this is accurate. It is a mathematical calc using an extremely short distance (couple of inches on the microphone stalk), and does not account for the entry angle of the trajectory.

Looking at the Litz / Applied Ballistics book, your 162gr SST has the following BC:

G1 : 0.535
G7 : 0.274

I also see that your zero atmospherics and those for when you are shooting are the same. Did you record actual atmospherics when you zeroed ?

Hi ebf - thanks for the info.

The 300 m vs yards would help explain it but there was a bit of chat about it on the day and we were definitely shooting 300m. Have redone the inputs heaps of times and used a few different apps and online calculators and my calculation zero is definitely set to 100m not yards. I didn't record actual atmospherics when zeroing, unfortunately.

100% agree that my scope height is not 3 inches. That was the only input adjustment that got me to 3MOA @ 300m, definitely not ideal but am hesitant to change MV to 3300 fsp to arrive at 3 MOA @ 300m.

Thanks for the G7 figure. Hornady doesn't publish a G7 so didn't have a reliable source. Changing it from .550 G1 to .274 G7 still gives me a solution of 3.98MOA @ 300m

Am wondering if the scope wasn't mounted correctly and that has something to do with it.

Did anyone actually range the distance or did they just chat and assume? Because the dial difference between 300Y and 300M is going to be pretty much near on 1 MOA like you are seeing.