The Impact of Losing Zero – Causes and Mitigation Strategies

[JPW13]

Hi everyone,

This forum is full of great information about the importance of maintaining zero on a rifle scope and how critical it is for accuracy, especially as ranges extend. I wanted to dive deeper into the potential sources of losing zero and strategies for addressing it.

Recently, I’ve been grappling with zero shifts in winter conditions and am curious about the main contributors. Could this be due to density altitude, powder sensitivity, or something else entirely? While ballistic solvers do a good job accounting for environmental variables like weather, it seems that if your zero is off, none of that matters.

In my case, I’m using a high-quality scope (NightForce) that should hold zero reliably. This got me thinking: could we theoretically limit the environmental impact by zeroing at a closer range, say 25 yards? The idea being that environmental factors (like temperature, density altitude, etc.) might play out sooner and have less overall effect.

Or is this too optimistic? Even with a scope that holds zero well, do we still need to check and adjust zero whenever there’s a significant environmental change, like a temperature swing or elevation shift?

I’d love to hear your thoughts, experiences, and suggestions on this topic. Are there best practices you follow for maintaining zero in variable conditions?

Thanks in advance for the insights.

 

[Axlrod]

In my experience, scopes that hold zero do so in any conditions you listed.

 

[JPW13]

In my experience, scopes that hold zero do so in any conditions you listed.

How is that possible when velocity is impacted by environmental conditions? FYI, I'm using an NX8, so I have confidence that the scope holds zero.

 

[Obsessed1]

Build your zero off larger group samples. Hornady guys have a great way of explaining zero angle. Likely what your seeing isn't a zero shift at all...as in not a scope issue..shot dispersion of a larger group size ( 20+ rounds) will likely show your zero to not be a true zero within the dispersal area of your group

 

[Axlrod]

How is that possible when velocity is impacted by environmental conditions? FYI, I'm using an NX8, so I have confidence that the scope holds zero.

Well there isn't going to be enough change in velo to impact your 100 yard zero. I have killed game from 75* to -54* without any point of impact issues. But you can test your own equipment in different conditions to see how it reacts. But I wouldn't worry too much about it.
If your NX8 has loss of zero, it most likely is not the scope or the conditions.
All my hunting guns, I zero and get a velocity average around 30*. This is probably close to the mean temp during general rifle season.

 

[77TMK]

How much of a change in zero are you experiencing?

 

[JPW13]

Build your zero off larger group samples. Hornady guys have a great way of explaining zero angle. Likely what your seeing isn't a zero shift at all...as in not a scope issue..shot dispersion of a larger group size ( 20+ rounds) will likely show your zero to not be a true zero within the dispersal area of your group

To provide some context, this is in my Tikka .223 with an NX8 2.5-20 scope mounted in UM Tikka rings, torqued with nail polish and witness-marked using a paint pen.

The rifle was zeroed with a 30-round group at 10°C (50°F). Today, at -8°C (17.6°F), my 10-shot group was 0.2 MIL low and 0.2 MIL right. Average velocity was 2800 fps compared to 2850 fps during the initial sight-in. The load consists of 77 TMKs over 26 grains of Leverevolution. All rounds—from the first sight-in to this most recent 10-shot group—came from the same batch of reloads, using the same lot of brass, bullets, and powder.

I don't believe the rifle system lost zero, given the quality of the equipment and how it was assembled. However, it seems plausible that environmental factors affected the zero. Or do people think that's not a thing?

 

[JPW13]

How much of a change in zero are you experiencing?

Shift of .2 down and right

 

[LR5Ranger]

Shift of .2 down and right

Could it be a bedding issue? I’m guessing all the screws mounting scope, rail etc were evenly torqued with a torque wrench?

 

[77TMK]

Are you shooting in the exact same position? What’s your velocity difference? Sounds like something is shifting POI from touching the barrel differently.

 

[DangerRanger]

How is that possible when velocity is impacted by environmental conditions? FYI, I'm using an NX8, so I have confidence that the scope holds zero.

I’ve seen loads in pressure testing cross 250 fps spread and still all go into the same 1.5 moa @ 100

 

[LeftyWilbury]

keep shooting. it's winter. over the next two months, does it change?
i dont like drawing conclusions when i'm shooting and it's stupid cold. all i can reasonably conclude is that i'm cold and not focusing.

 

[LR5Ranger]

Maybe the parallex isn’t quite on and you have additional clothing changing your cheek weld slightly?

 

[mt100gr.]

How thick of a jacket were you wearing at 50°?

 

[Parkerpusher]

Maybe the parallex isn’t quite on and you have additional clothing changing your cheek weld slightly?

I would guess this is it. More clothing is going to make you mount differently. Try stripping the jacket for a quick 5 rd group?

 

[77TMK]

Also a 30rnd group will heat your barrel to the point of a POI shift. It seems ridiculous tbh.

 

[JPW13]

So, what I’m gathering here is that no one believes environmental conditions can impact a 100m zero? I agree that the most likely issue is user error (me). That being said, this wasn’t the only rifle I was shooting. Another example, zeroed in colder temperatures and using a more “temperature-insensitive” powder, was unaffected.

If the issue was my puffy jacket or an inability to properly set parallax, wouldn’t that have shown up with the other rifle as well? Additionally, once I re-zeroed the .223, I was able to continue my range day, ringing steel consistently from 500 to 800m.

If the problem were a loose or over-torqued nut behind the gun, wouldn’t that have continued to show itself at range—if not become even more obvious?

 

[77TMK]

So, what I’m gathering here is that no one believes environmental conditions can impact a 100m zero? I agree that the most likely issue is user error (me). That being said, this wasn’t the only rifle I was shooting. Another example, zeroed in colder temperatures and using a more “temperature-insensitive” powder, was unaffected.

If the issue was my puffy jacket or an inability to properly set parallax, wouldn’t that have shown up with the other rifle as well? Additionally, once I re-zeroed the .223, I was able to continue my range day, ringing steel consistently from 500 to 800m.

If the problem were a loose or over-torqued nut behind the gun, wouldn’t that have continued to show itself at range—if not become even more obvious?

0.2 mil right and down shift is 3/4”. That’s not environmental at 100 yards when the temperature delta is 30 F.

 

[Parkerpusher]

So, what I’m gathering here is that no one believes environmental conditions can impact a 100m zero? I agree that the most likely issue is user error (me). That being said, this wasn’t the only rifle I was shooting. Another example, zeroed in colder temperatures and using a more “temperature-insensitive” powder, was unaffected.

If the issue was my puffy jacket or an inability to properly set parallax, wouldn’t that have shown up with the other rifle as well? Additionally, once I re-zeroed the .223, I was able to continue my range day, ringing steel consistently from 500 to 800m.

If the problem were a loose or over-torqued nut behind the gun, wouldn’t that have continued to show itself at range—if not become even more obvious?

In my experience, environment is not impactful enough at 100 to be noticeable unless crazy windy. Rimfire is an exception.

 

[JPW13]

Could it be a bedding issue? I’m guessing all the screws mounting scope, rail etc were evenly torqued with a torque wrench?

Yes. Everything was torqued to spec.