Looking for help. Shooting low

[Paul Milone]

Im looking for any help with this issue / question. I recently had a build completed by a quality gunsmith / national shooter. It's a Rem 700 action, 26" Stainless Proof Research barrel, 6.5 creedmore, Razor HD Gen II 4.5-27x56, LaRue Tactical OBR mount/rings, 20 MOA base, Hornady 140gr ELD-M rounds. Timney trigger

Shooting sub 1" at 100. Ballistics calculator(s) all say I should be 2.6 mills at 500. I was not on steel until I went up to 4.1 mills A full 1.5 mills more. Then I shot a hurried 5" 5 shot group at 500yds.

Wondering what was going on. What did I do wrong. Re calculated the ballistics program(s), re sighted in.... no change.

Shot 10 rounds thru decent chronograph. Averaging 2797 fps.

Took scope off, replaced it with a Nightforce. Got the same results, shooting low, but shooting tight.
I spoke with the folks at Proof Research. I spoke with the gunsmith, I spoke with great shooters. All say dont worry about it, just increase your dope and continue to shoot groups at distance.....

Some other folks say "it's a lemon".

Has anyone else had a barrel that "shoots low" ?

 

[GrocMax]

Lower the BC in the calculation till it matches your result.

 

[Sniper338]

This dont sound like a gun problem. Sounds like a data and ballistic calculator issue.

The guns is gonna shoot how it shoots.

Ballistic calculators arent fool proof. The output is only as good as the input and still there is a margin or error.

A ballistics app will NEVER be better than raw feild data you collect yourself. Slope of the shot will change the dope

 

[Sniper338]

I have a notebook for each of my rifles i keep data on evertime i go shoot. I record range, slope, wind, ambient temp, humidity, degree of direction, etc etc etc

 

[savagedasher]

Scope hight . It does the same a peep hight with a bow . Larry

 

[GrocMax]

Scope height measurement off by 2" ain't gonna be 1.5 mils at 500. There's some bad data somewhere.

 

[M995]

What BC did you use

 

[savagedasher]

Scope height measurement off by 2" ain't gonna be 1.5 mils at 500. There's some bad data somewhere.

Sorry I can't agree . My vxl with with low mounts on my 300 wby sight in at 100 And tall mounts the difference at 600 was over 7 moa . The number I use was the same as I used at 600 for 1000 yards
It's the no different then a peep is on a bow .
Larry

 

[GrocMax]

You're wrong. 1.5 mils at 500 yds is 24" plus.

 

[BoydAllen]

If you run a ballistic program with a couple of different scope heights, that are quite a bit different, I think that you will see that it makes a lot more difference than most would believe. The other thing that I would do is to verify my scope adjustments to see if they are what they are marked.

 

[Paul Milone]

If you run a ballistic program with a couple of different scope heights, that are quite a bit different, I think that you will see that it makes a lot more difference than most would believe. The other thing that I would do is to verify my scope adjustments to see if they are what they are marked.

When I changed from the vortex(mills) with a 2.5" scope height to the night force (MOA) 1.5" scope height it made no difference. I was still off 2 full MOA low.

When the Vortex was on at 500 I was 1.5 mills low. After I grouped at 500, I dialed back to zero and held 4.2 mills in the reticle and got hits just like when I dialed it. So the adjustments seem to be true.

I have re entered the data a dozen times thru "Shooter" and verified it thru Strelok and the numbers do not change. I've had accomplished shooters enter my data for me. No different results. Everyone is confused by it like you guys.

I plan on simply using my original Virtex and use actual raw data to build my DOPE and say the heck with the calculators

 

[GrocMax]

Ok, let's do that. JBM Ballistics calculator. 264 Hornady ELD-M with their stated G7 BC, 2800 fps, 100 yd zero.


1.0" scope height.

500 yds = -2.9 mils

2.0" scope height

500 yds = -2.7 mils.

He states he is off by 1.5 mils at 500 yds.

There's some bad data but being off +/- 1/8" in scope height isn't it.

 

[Paul Milone]

Scope height measurement off by 2" ain't gonna be 1.5 mils at 500. There's some bad data somewhere.

When I changed from the vortex(mills) with a 2.5" scope height to the night force (MOA) 1.5" scope height it made no difference. I was still off 2 full MOA low.

When the Vortex was on at 500 I was 1.5 mills low. After I grouped at 500, I dialed back to zero and held 4.2 mills in the reticle and got hits just like when I dialed it. So the adjustments seem to be true.

I have re entered the data a dozen times thru "Shooter" and verified it thru Strelok and the numbers do not change. I've had accomplished shooters enter my data for me. No different results. Everyone is confused by it like you guys.

I plan on simply using my original Virtex and use actual raw data to build my DOPE and say the heck with the calculators

 

[Paul Milone]

Lower the BC in the calculation till it matches your result.

I had to go down to .1800 ish.

 

[BoydAllen]

Is there a bc that makes it all work as it should? Perhaps the bullet manufacturer has been more than a bit "optimistic".

 

[Paul Milone]

This dont sound like a gun problem. Sounds like a data and ballistic calculator issue.

The guns is gonna shoot how it shoots.

Ballistic calculators arent fool proof. The output is only as good as the input and still there is a margin or error.

A ballistics app will NEVER be better than raw feild data you collect yourself. Slope of the shot will change the dope

When I changed from the vortex(mills) with a 2.5" scope height to the night force (MOA) 1.5" scope height it made no difference. I was still off 2 full MOA low.

When the Vortex was on at 500 I was 1.5 mills low. After I grouped at 500, I dialed back to zero and held 4.2 mills in the reticle and got hits just like when I dialed it. So the adjustments seem to be true.

I have re entered the data a dozen times thru "Shooter" and verified it thru Strelok and the numbers do not change. I've had accomplished shooters enter my data for me. No different results. Everyone is confused by it like you guys.

I plan on simply using my original Virtex and use actual raw data to build my DOPE and say the heck with the calculators

 

[GrocMax]

Shooting at two distances should get you a lot closer to true BC for your situation. Sounds like you've double checked all the other data.

What's the barrel twist? Is it under stabilized?

This may sound silly but is it possible the 20 MOA rail is on backwards?

 

[Paul Milone]

Is there a bc that makes it all work as it should? Perhaps the bullet manufacturer has been more than a bit "optimistic".

Hornady is usually good stuff. A friend of mine is shooting an almost exact replica gun and scope and shoots the exact ammo ( Hornady ELDM 140gr). He hits where the ballistics calculators say he should... 2.6 at 500

So I don't think it's an ammo problem

 

[SheepDog]

Accept what you get on the target. The target is always right! Software, and I have written two ballistics programs, is an approximation of where your bullet will be. That's the best you can get from software. The real world demands that you shoot at the different ranges and record them in your DOPE sheet. The software lives in a perfectly digital world. We shoot in a three dimensional analog world.

 

[GrocMax]

Having to adjust a G7 BC by that much (.305 to .180) doesn't add up. A tenth or two but not that much. 500 yds is short range for a ballistics calc, before the rainbow, something doesn't add up in a big way.