.223 ballistic mystery...

[bellavite1]

Vortex Viper hs, MOA turrets.

[Grant H.]

I will bet $20 that your optic height is what you are fighting.

Irons are 1.4", and a lot of optics mounts shoot for that same level (cowitness). The 25/200 zero is built around irons. Having to account for the additional 1.2" in optic height means that the angle of convergence between bore and optic is more aggressive. This could easily explain the additional 1" @ 100yds.

[Tim K]

I see at least two problems. As Ray pointed out, your velocity is a guess. Secondly as Chick pointed out, accuracy is pretty poor. I’m not trying to bust your chops, but it’s hard to tell anything from a 3”-4” 100y group.

It could also EASILY be a parallax issue with your scope. If your scope is fixed parallax, it’s most likely set at 100y. At 50 and 200y it could be far enough off that subtle inconsistencies in head position could account for all your error. Might even account for some of your accuracy issues. If parallax is adjustable and you don’t know how to use it correctly, that would cause all the same problems.

[bellavite1]

I will bet $20 that your optic height is what you are fighting.

Irons are 1.4", and a lot of optics mounts shoot for that same level (cowitness). The 25/200 zero is built around irons. Having to account for the additional 1.2" in optic height means that the angle of convergence between bore and optic is more aggressive. This could easily explain the additional 1" @ 100yds.

I am using a pretty standard ar mountm and I am pretty sure it cowitness.
To clarify, 2.6" id measured from center bore to optical center, as in the picture.
And it is programmed into the ballistic app as well, so it is factored in.

[bellavite1]

I see at least two problems. As Ray pointed out, your velocity is a guess. Secondly as Chick pointed out, accuracy is pretty poor. I’m not trying to bust your chops, but it’s hard to tell anything from a 3”-4” 100y group.

It could also EASILY be a parallax issue with your scope. If your scope is fixed parallax, it’s most likely set at 100y. At 50 and 200y it could be far enough off that subtle inconsistencies in head position could account for all your error. Might even account for some of your accuracy issues. If parallax is adjustable and you don’t know how to use it correctly, that would cause all the same problems.

No offense taken!
However, I would like to point out that both 100 yds pictures show a vertical spread of about 1.5 MOA (hardly something to be proud of, but somewhat within specs for an average AR from what I hear).
There is consistency there.
The white and orange target is a 200 yds target, shot with the 50 yds zero, without any elevation adjustment, to show that the 50/200 zero actually pans out.
I do appreciate all the replies, but I still don't see how this additional 1" of correction from 50 to 100 comes to be.

[Grant H.]

I am using a pretty standard ar mountm and I am pretty sure it cowitness.
To clarify, 2.6" id measured from center bore to optical center, as in the picture.

Yep, I grabbed the wrong number off the drawing.

[bellavite1]

I see at least two problems. As Ray pointed out, your velocity is a guess. Secondly as Chick pointed out, accuracy is pretty poor. I’m not trying to bust your chops, but it’s hard to tell anything from a 3”-4” 100y group.

It could also EASILY be a parallax issue with your scope. If your scope is fixed parallax, it’s most likely set at 100y. At 50 and 200y it could be far enough off that subtle inconsistencies in head position could account for all your error. Might even account for some of your accuracy issues. If parallax is adjustable and you don’t know how to use it correctly, that would cause all the same problems.

The scope has parallax adjustment and I do adjust it for range.
I have the same scope (well, Viper PST) on my other rifles and they all shoot consistent with the ballistic tables, from the 308 to the 50BMG.
This one is the only one that doesn't...

[C Ward]

A few things ,

Barrel length has got jack to do with anything other than it's affect on velocity

If the 1st target is 50 yards it is shooting 4 MOA which make diagnosing accuracy issues pretty much impossible , even blaster ammo typically shoots better than that

How is the scope mounted , is it all on the receiver or is it jumping the gap and on a receiver and free float tube

Sight height / scope height is not an issue after the 1st cross over point after the cross over point the ballistic curve determines the height above or below the line of site

The 1st target also looks like it is possibly showing 2 seperate groups , 1 at the top with 2 rds and 1 at the bottom with 3 rounds , signs of rear bag cheek pressure issues

1st thing is get ammo that shoots better than 4 moa that actually groups . The bottom 2 targets show groups wider than tall which can be a few things , NPA , trigger control , muscling the gun

Check the scope mounting , tight fasteners , binding , interference, DO NOT BRIDGE THE GAP WITH THE MOUNT

The viper is lower end Vortex and has been hit or miss quality , check the tracking and make sure it is functioning correctly

At 2.6 inch scope your more than likely going to need a cheek riser to get a consistent cheek weld

[Great-Kazoo]

Outside of the front bag, use a squeeze bag on that buttstock. Minimalizes movement.
https://www.crosstac.com/shop-all-pr...r-squeeze-bag/

OR use a lead sled to really take all the human error / movement out of the equation. Or as much as possible .

[bellavite1]

A few things ,

Barrel length has got jack to do with anything other than it's affect on velocity

If the 1st target is 50 yards it is shooting 4 MOA which make diagnosing accuracy issues pretty much impossible , even blaster ammo typically shoots better than that

How is the scope mounted , is it all on the receiver or is it jumping the gap and on a receiver and free float tube

Sight height / scope height is not an issue after the 1st cross over point after the cross over point the ballistic curve determines the height above or below the line of site

The 1st target also looks like it is possibly showing 2 seperate groups , 1 at the top with 2 rds and 1 at the bottom with 3 rounds , signs of rear bag cheek pressure issues

1st thing is get ammo that shoots better than 4 moa that actually groups . The bottom 2 targets show groups wider than tall which can be a few things , NPA , trigger control , muscling the gun

Check the scope mounting , tight fasteners , binding , interference, DO NOT BRIDGE THE GAP WITH THE MOUNT

The viper is lower end Vortex and has been hit or miss quality , check the tracking and make sure it is functioning correctly

At 2.6 inch scope your more than likely going to need a cheek riser to get a consistent cheek weld

Now we may be getting somewhere...
Scope is mounted correctly, all on the receiver, not bridging the gap, 35 pounds on the crossbolts, 15 pounds on the caps.
Cheek weld feels right, natural, but I did notice that it seems to shoot better at 100 than at 50, with the shooting position being elevated over the targets, so that the 50 yds requires more of an angle, potentially creating cheek pressure issues.
I will try a more leveled position, with better bullets (Midway has Sierra MK 69 gr at a decent price, free shipping over $49) and then report...