Shot groups and ballistic data don't match

[junkyard.brody]

Let me start by saying that I am not a new shooter and have mitigated every variable that I can think of. I mainly use my Kestrel 5700 and have also used Strelok Pro. I am shooting a 6.5 Creedmoor with 140 ELD-M handloads. (40.8gr H4350, CCI 200 and Nosler brass). The bullet is going roughly 2700 with low SD and ES. The bullet has a G7 BC of .326 according to Hornady's newest BC chart. The bullet is seated 5thou off the lands and produces a ragged hole group at 100. My rifle setup is a 24" Bartlein barrel, KRG Whiskey 3, TT Diamond and Leupold Mark 5 5-25 with a griffin armament scope mount. I also have a magnetospeed V3 and have trued my BC at 1000 but it always shoots low everywhere inbetween 100 and 1000.

The problem that I am having is that for my ballistic data to be accurate, my 100 yd zero needs to be .2 mil low at 100 yards.

Today my ballistic data said I needed to be 1.3 mil at 300, so I shot a group and slipped my turret from 1mil to 1.3 mil at 300. I then proceeded to shoot 4,5,6,7,8 and 1000 yds with no issues in my ballistic data. I then dialed back down to my true zero and shot a 100yd group and it was .2mil low. It is not a big issue since I rarely shoot less than 300 but I'm curious if anyone knows what might be the cause. Thanks.

 

[Dthomas3523]

It’s either you while shooting (pushing rifle down or something) or you haven’t properly trued your software.

Mess with MV and BC until center of your groups center on waterline at each distance as well as being zero’d properly.

 

[junkyard.brody]

I figured it’s something that I’m doing but I don’t understand how I’m getting consistent results by either being dead on at 100 and high everywhere else or low at 100 and dead on everywhere else. I went and shot this morning and sprayed a line on the steel and after I adjusted my zero, all of my groups were on the line.
I guess I’ll mess with my calculator some more.

 

[junkyard.brody]

I accidentally said low in the thread but I actually mean it shoots high.

 

[_Windrider_]

Sounds to me like your zero has changed or it wasn’t done properly. You can also account for that zero offset in the software and that should fix it.
Remember the bullet is the truth. You have to make the calculator equal what the bullet actually does.

 

[whatsupdoc]

Are you sure you are at 100 yards when you zero?
I did that at a public range and it was 98 yards not 100.

 

[sinister]

The bullet has a G7 BC of .326 according to Hornady's newest BC chart.

You are assuming Hornady's data is identical to your rifle, ammo, and conditions.

Have you compared it to another set of software (maybe JBM Ballistic, free on-line)?

 

[junkyard.brody]

Sounds to me like your zero has changed or it wasn’t done properly. You can also account for that zero offset in the software and that should fix it.
Remember the bullet is the truth. You have to make the calculator equal what the bullet actually does.

I agree that the bullet doesn’t lie. Which is why it doesn’t make sense that my drop is true past 300 but not at 100.

 

[junkyard.brody]

You are assuming Hornady's data is identical to your rifle, ammo, and conditions.

Have you compared it to another set of software (maybe JBM Ballistic, free on-line)?

I’ve been messing with my bc to get it trued for the last week. Basically when my zero is dead on at 100 and I true the BC at 1000, I shoot high everywhere in between there. Or what I did today is slip my turret to 1.3 mils at 300 (which is what my data is telling me it should be) and I’m dead on at every distance out to 1000 but I’m .2 mils low at 100. I’ll look at JBM Ballistic though.

 

[pell1203]

Have you confirmed the turrets on the scope are running true via a tall target test?

 

[Dthomas3523]

Are you sure you are at 100 yards when you zero?
I did that at a public range and it was 98 yards not 100.

You have to be 15+ (more really) difference at 100 yds for it to be different.

This is one of the biggest myths perpetuated. 98 vs 100 with a centerfire doesn’t matter.

 

[BrienM]

I wonder if the scope height setting in your app is correct?

 

[seansmd]

I don't see in your original post where you trued your MV at 600y?

Solid zero, measured sight over bore
True muzzle velocity at 600y
True BC @1000+

 

[padom]

I agree with the above, are you sure your height over bore is correct? You also say your bullet is "going roughly" 2700 with low ES/SD. What does roughly mean? Did you chrono this load with 20-25rd and use that exact number in your Kestrel???

Also, when you setup your Gun/Profile initially in your Kestrel, when selecting the bullet from the Library did you select G1, G7 or AB Custom Curve? I always select the AB Custom Curve and just put in velocity, zero distance and height over bore and its always dead on..

 

[junkyard.brody]

@BrienM was right. I was talking to buddy last night and he suggested changing the bore height and that took care of it.

 

[padom]

@BrienM was right. I was talking to buddy last night and he suggested changing the bore height and that took care of it.

I see people not imputing the correct height over bore a lot and having issues with dope not lining up. Its important. Glad you got it figured out!

 

[junkyard.brody]

I agree with the above, are you sure your height over bore is correct? You also say your bullet is "going roughly" 2700 with low ES/SD. What does roughly mean? Did you chrono this load with 20-25rd and use that exact number in your Kestrel???

Also, when you setup your Gun/Profile initially in your Kestrel, when selecting the bullet from the Library did you select G1, G7 or AB Custom Curve? I always select the AB Custom Curve and just put in velocity, zero distance and height over bore and its always dead on..

Is the AB custom curve only on the elite? I just have the 5700 and it doesn't pop up under drag model.

 

[padom]

Is the AB custom curve only on the elite? I just have the 5700 and it doesn't pop up under drag model.

Ah gotcha....I have a 5700 elite AB Bluetooth so I guess so..

 

[junkyard.brody]

I'm sure this isn't the case but I gotta ask. Are you zeroing your rifle with the chrono on your barrel?

My barrel is MTU contour and I haven’t noticed a big POI shift with my magnetospeed on or off. But yes I verify my zero after taking the chrono off.