Truing BC and MV

[H80Hunter]

Can anyone help me with this process? I generally use the Hornady app. What I've been doing is the following:

1) Zero at 100 yards
2) Back up to 200 yards, tweak MV in the app to align the predicted drop to what I saw.
3) Back up to 500 yards. Here's where I get stuck, as if I make some changes here to the MV in the app it seems to throw my 200 yard data off. Maybe not by a significant amount but a couple clicks anyway. I tend to find even with a 100 yard zero, and 200 yard drop confirmed I tend to be shooting like an MOA lower than predicted in the app at 500. If I lower the MV in the app to get the 500 yard drop matched up, I then seem to be high at 200.

What's the right process or this? I was thinking to tweak the MV at 200 and then the BC at 500. I assume the MV will have a bigger effect at 200 than BC, and the BC should be more important at 500 than the MV, but that's just a hunch. Also, tweaking the BC changes my windage holds. I know there's no substitute here for trigger time, but any ideas or summaries you can link to to more efficiently approach this would be appreciated.

 

[Antares]

I zero at 100 and then look at my 300 and 500 yard drops. There's no need to mess with BC at those ranges. You should be able to get really close with MV alone, something is wrong if not. Your going to need to accept some deviation, just try to find a happy middle ground. If you're using the 4DOF portion of the Hornady app, you can fiddle with the axial form factor, but if you find yourself making big adjustments that tells me something is off. I generally do not mess with form factor.

How are you getting your atmospherics?

 

[Formidilosus]

Can anyone help me with this process? I generally use the Hornady app. What I've been doing is the following:

1) Zero at 100 yards
2) Back up to 200 yards, tweak MV in the app to align the predicted drop to what I saw.
3) Back up to 500 yards. Here's where I get stuck, as if I make some changes here to the MV in the app it seems to throw my 200 yard data off. Maybe not by a significant amount but a couple clicks anyway. I tend to find even with a 100 yard zero, and 200 yard drop confirmed I tend to be shooting like an MOA lower than predicted in the app at 500. If I lower the MV in the app to get the 500 yard drop matched up, I then seem to be high at 200.

What's the right process or this? I was thinking to tweak the MV at 200 and then the BC at 500.

No. Do not mess with BC unless you are shooting a Hammer. And there is zero reason to do anything at 200 yards.

I assume the MV will have a bigger effect at 200 than BC, and the BC should be more important at 500 than the MV, but that's just a hunch. Also, tweaking the BC changes my windage holds. I know there's no substitute here for trigger time, but any ideas or summaries you can link to to more efficiently approach this would be appreciated.

Zero at 100 with a 10-20 round group totally centered over POA. Then go straight to the farthest range you have that is above 1,340fps’ish impact speed- or 500 yards if that’s all you have. Make sure there is little to no wind and that you have the correct environmental data. Guess at MV or put your measured MV in the app and then shoot at that range. Adjust the elevation MOA/mil until the center of the group is splitting the center of the target vertically- do not worry about horizontal spread as long as the rounds are on target. Shoot a group of 10’ish rounds to confirm POI. Adjust MV in app until the data provided matches your real drop.

 

[Lawnboi]

If you’re having to make any adjustment on one of the big solvers at 500 yards you need to start looking at your equipment. It screams scope issue to me.

Iv yet to have a rifle that I can’t take the bc off the box, get a MV with my Labradar and be within my cone of fire at 500 yards.*shooting popular bullets

 

[H80Hunter]

Could be a slight zero offset, I’ll shoot more rounds to confirm it.

And I’m only talking like, 100 yard zero, get drop at 500, then it puts my 200 yard and inch high. I’m not saying it takes me way off into no man’s land.

 

[XLR]

Truing Rifle Data

This is the time of the year when shooters start getting the itch. It is the best time to start brushing up on your wind calls and making sure that your rifle is shooting well! One common question that we get asked is how we true our data when we gather dope. This is a great question because...

xlrindustries.com

Take a look at this.

 

[willfrye027]

Could be a slight zero offset, I’ll shoot more rounds to confirm it.

And I’m only talking like, 100 yard zero, get drop at 500, then it puts my 200 yard and inch high. I’m not saying it takes me way off into no man’s land.

Sounds like a slight zero error at 100 if it’s consistently doing that. Or shooting form/bag/bipod issue maybe if you confirm accurate zero at 100 and accurate drops at 500.

 

[BjornF16]

No. Do not mess with BC unless you are shooting a Hammer. And there is zero reason to do anything at 200 yards.

What if it is a Hammer bullet?

 

[Formidilosus]

What if it is a Hammer bullet?

Their BC’s are generally inflated enough to cause relatively large errors. If you are going to shoot them past 400’ish yards, I would get a legit zero at 100 yards, get average MV from at least 30 shots, then go to the maximum range you will shoot, and get a 20 round group on paper, find center and then adjust BC to match at that range.

 

[ATL]

Ensure the distances are correct, 100 and 500 yards respectively. If the 500 yard berm at your range is actually 492y, or 511y for example, that will need to be accounted for in the ballistic program.

A tall target will shed interesting information as well, isolating/identifying possible scope tracking errors. Place a target at the top of a tall target stand and shoot a group at exactly 100 yards with your 100 yard zero set.

Then move that target and stand to exactly 500 yards, and shoot another group while aiming at the original target with your 100 yard zero set (do not dial away from your 100y zero). The bullets will impact paper well below the target. For my rifle I would expect an approx. 46” drop at 500 yards from the 100 yard impacts, so make sure you have paper set up below the target far enough to catch the impacts.

Measure the difference between the two groups to get the actual bullet drop between 100 and 500 yards. Divide the drop by 5.235 if using a MOA based scope, or 18 for MILS. Let’s assume for my rifle the actual measured drop at 500 yards was 46”:

46 / 5.235 = 8.78 MOA (round to 8.75)
46 / 18 = 2.55 MIL (round to 2.6)

If my ballistic program’s prediction matches it is calibrated correctly.
If when I dial these corrections in to the scope and my actual impact is way off, I likely have a scope tracking issue.

 

[huntnful]

What if it is a Hammer bullet?

Their BC’s are generally inflated enough to cause relatively large errors. If you are going to shoot them past 400’ish yards, I would get a legit zero at 100 yards, get average MV from at least 30 shots, then go to the maximum range you will shoot, and get a 20 round group on paper, find center and then adjust BC to match at that range.

It’s pretty safe to just knock .03 off the G7 from their advertised BC’s. I have not found a single bullet that has been closer to advertised than that. And I’ve shot a lot of them.

 

[Muley Buck]

No. Do not mess with BC unless you are shooting a Hammer. And there is zero reason to do anything at 200 yards.






Zero at 100 with a 10-20 round group totally centered over POA. Then go straight to the farthest range you have that is above 1,340fps’ish impact speed- or 500 yards if that’s all you have. Make sure there is little to no wind and that you have the correct environmental data. Guess at MV or put your measured MV in the app and then shoot at that range. Adjust the elevation MOA/mil until the center of the group is splitting the center of the target vertically- do not worry about horizontal spread as long as the rounds are on target. Shoot a group of 10’ish rounds to confirm POI. Adjust MV in app until the data provided matches your real drop.

@Formidilosus What do you suggest when you have a confirmed zero at 100 yds then have also confirmed at 800 yds that vertical is good as well, but then at 500 yds my all my shots are high misses? I cannot seem to figure out why this is happening.

 

[rileybassman]

@Formidilosus What do you suggest when you have a confirmed zero at 100 yds then have also confirmed at 800 yds that vertical is good as well, but then at 500 yds my all my shots are high misses? I cannot seem to figure out why this is happening.

Scope tracking? What scope you using?

Sent from my SM-G991U using Tapatalk

 

[H80Hunter]

I am the OP and saw this thread come back up. I think I should post that Form was unsurprisingly correct. Shooting more rounds highlighted that the issue was basically sample size related. My 100 yard zero was off slightly was basically the entire issue.

 

[Reburn]

I am the OP and saw this thread come back up. I think I should post that Form was unsurprisingly correct. Shooting more rounds highlighted that the issue was basically sample size related. My 100 yard zero was off slightly was basically the entire issue.

This is exactly the gist of the hornady podcast your groups are too small. They demonstrate this when someone talks about a $4 a round mag being expensive to shoot 10 round groups.

 

[Muley Buck]

Scope tracking? What scope you using?

Sent from my SM-G991U using Tapatalk

It is possible that it could be a tracking issue and I won't deny it if it actually is, but it repeatedly has done this the last 3 outings. Tracks fine to 800 yds and back down to 100 yds with no POI shift. I'm talking minimum 10-15 rounds at each range. But at 520 yds to be specific I'm consistently shooting 2 MOA high according to what my range finder is telling me. I've never experienced this before. Everyone will probably write off this post now because I have to say I am using a Vortex scope it's an AMG. If it is in fact a scope issue I have no problem accepting that and rectifying the issue. I would like to get to the bottom of this and fix it though.

 

[Reburn]

It is possible that it could be a tracking issue and I won't deny it if it actually is, but it repeatedly has done this the last 3 outings. Tracks fine to 800 yds and back down to 100 yds with no POI shift. I'm talking minimum 10-15 rounds at each range. But at 520 yds to be specific I'm consistently shooting 2 MOA high according to what my range finder is telling me. I've never experienced this before. Everyone will probably write off this post now because I have to say I am using a Vortex scope it's an AMG. If it is in fact a scope issue I have no problem accepting that and rectifying the issue. I would like to get to the bottom of this and fix it though.

I'll just leave this pearl here.
My guns never grouped consistently better and my hit rate went up when I put scopes on that are known performers.
I even replaced a barrel on a 6.5 grendel once that didnt group. Wasnt till later I realized it was the vortex pst.....

I cant see how you could be 2 moa high at 520 and nowhere else though.

 

[Muley Buck]

I'll just leave this pearl here.
My guns never grouped consistently better and my hit rate went up when I put scopes on that are known performers.
I even replaced a barrel on a 6.5 grendel once that didnt group. Wasnt till later I realized it was the vortex pst.....

I cant see how you could be 2 moa high at 520 and nowhere else though.

I know, I keep thinking exactly what you are saying. I'll probably end up ripping it off and getting an NX8 on it. SMH.

That mid range is what is perplexing to me.

 

[Formidilosus]

@Formidilosus What do you suggest when you have a confirmed zero at 100 yds then have also confirmed at 800 yds that vertical is good as well, but then at 500 yds my all my shots are high misses? I cannot seem to figure out why this is happening.

If you are positive of your 100 zero, and 800 impact centered, and your inputs in your data is correct- then it’s a scope adjustment issue. Not much else it could be. Swap scopes and see.

 

[swavescatter]

@Formidilosus What do you suggest when you have a confirmed zero at 100 yds then have also confirmed at 800 yds that vertical is good as well, but then at 500 yds my all my shots are high misses? I cannot seem to figure out why this is happening.

Spitballing here but I could imagine a ballistic solution that matches at two end points but is fudged in the middle, maybe.

What if your scope above bore/scope rail cant is wrong? You could be getting a solution at 800 that thinks your bullet arc is flatter than it is?

I'm a relative newb but it seems like this could be plausible if your inputs are off.