The Impact of Losing Zero – Causes and Mitigation Strategies

[Machingeaneer]

How about stock to action? Torqued to 65 in/lbs?

 

[JPW13]

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

More of a .15 right but I adjusted .2 and that put the group slightly left.

But the down was definitely a solid .2. It sounds like you’re a least open to the idea that the conditions could impact the zero?

Is it possible leverevolution is effected by temp. It’s a new powder to me. Looking forward to your thoughts.

 

[77TMK]

All powders are sensitive to temperature and you simply need to record velocities at multiple, if not numerous increments of temperature to make a curve.

I am not sure why you zero with a 30 rnd group and check it with 10.


Also idk wtf you are doing with this 1.5 right shenanigans.

 

[SDHNTR]

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?

It’s not a .2mil at 100 kind of measurable thing! You have something else happening.

 

[JGRaider]

If it were a Leupold scope you'd have 40 people telling you it was a scope problem.

 

[mtnwrunner]

If it were a Leupold scope you'd have 40 people telling you it was a scope problem.

Totally unnecessary comment.

Randy

 

[JPW13]

All powders are sensitive to temperature and you simply need to record velocities at multiple, if not numerous increments of temperature to make a curve.

I am not sure why you zero with a 30 rnd group and check it with 10.


Also idk wtf you are doing with this 1.5 right shenanigans.

Can you help me with what you think I’m doing wrong and the subsequent shenanigans?

Most rifles I shoot a 10round to zero, but 223 is cheap and it’s supposed to be a one time thing; so I shot a full 30 round and zeroed to that cone of fire. Today in colder weather my ballistic solution at 500 (usually my litmus test for my rifles when I hit the range) wasn’t connecting. Couple rounds at 100 “confirmed” it was outside of cone of fire. But, “hey could be me” my puffy jacket, a hasty parallax adjustment, cold fingers. SO, I shot a 10 round to get a “true” sense of my zero. That cone of fire center as measured in my scope was .2mil low and somewhere between .1 and .2 left. So I’m estimated .15. Not sure that qualifies as “shenanigans”?

 

[Parkerpusher]

if you shot “a full 30 round” for your original zero, how did you get a good shooting position built with the 30 rd mag? Or did you have a good solid position with multiple shorter mags?

 

[NRA4LIFE]

I don't get this. I have an old Redfield Tracker on a 270 I keep in MO (I live in WA) that I use on the deer hunt every year that I have not adjusted in 25+ years. I have a short 50 yard rifle range on my place and my one shot test before the season have hit the same hole forever. Now, I understand I am not shooting at 600 yards, but I have hit and killed every deer I have shot at in that time period. Not bragging, just confused on zero drift on newer scopes.

 

[JPW13]

if you shot “a full 30 round” for your original zero, how did you get a good shooting position built with the 30 rd mag? Or did you have a good solid position with multiple shorter mags?

Hahaha I’m in Canada. At this point I’m lucky I’m not having to single feed .

But yes multiple mags and what I considered a pretty solid position.

Additional context: I shot the zero group probably 2 months ago and have been to the range frequently since that time shooting lots of 200-860M steel. Gun has been a solid performer up to this morning. Only obvious change was the weather.

 

[mt100gr.]

Hahaha I’m in Canada. At this point I’m lucky I’m not having to single feed .

But yes multiple mags and what I considered a pretty solid position.

Additional context: I shot the zero group probably 2 months ago and have been to the range frequently since that time shooting lots of 200-860M steel. Gun has been a solid performer up to this morning. Only obvious change was the weather.

You adjusted the scope to this new zero, correct?

If so, I would go through a few range trips, various shooting positions, etc before you touch it again. And this might mean just banging on the 100m target a bunch, which isn't as fun, I know. But getting a lot of rounds in varying conditions will probably tell you more.

I've done this myself, with a NF scope - I'd rezero to some error and then the next time it'd be closer to where it started the time before. Ultimately, best I could tell, it was an issue of me, shooting positions, hand positions, me, parallax, cheek weld, me, trigger control, bipod load, me, mirage, rear rest, me....and way down the list is environmental factors/field conditions.

Good luck!

 

[JPW13]

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

Isn't there a whole thread on here where @Formidilosus showed the data about cold bore vs hot not really being a thing? I also don't think anyone shooting a 30 round group is rapid firing? I know, I didn't; I took my time and my 1.2 MOA group seemed to be a pretty good bell curve where most were falling comfortably under 1MOA and that's held shooting it short and long (until today).

 

[JPW13]

You adjusted the scope to this new zero, correct?

If so, I would go through a few range trips, various shooting positions, etc before you touch it again. And this might mean just banging on the 100m target a bunch, which isn't as fun, I know. But getting a lot of rounds in varying conditions will probably tell you more.

I've done this myself, with a NF scope - I'd rezero to some error and then the next time it'd be closer to where it started the time before. Ultimately, best I could tell, it was an issue of me, shooting positions, hand positions, me, parallax, cheek weld, me, trigger control, bipod load, me, mirage, rear rest, me....and way down the list is environmental factors/field conditions.

Good luck!

Thanks for the input! Yes, I adjusted the scope to the new zero after noticing the shift. I plan to take your advice and put in some range time at 100m under various conditions before making any further changes. I agree that isolating the potential variables—especially the “me” factors like cheek weld, parallax, trigger control, and bipod load—will help narrow things down.

That said, I shot a few other rifles today under the same conditions, and none of them showed any zero shift. They performed as expected, hitting where I aimed when I applied the ballistic solution. I didn’t need to recheck zero on any of them, which makes this .223’s behavior stand out.

It’s possible there’s something unique about this setup—or maybe I’m just more inconsistent with it—whatever the case it was the outlier today, but it's odd that the other rifles were more closely zeroed to the same environmentals and had no issues, this one would have had the greatest change from zeroing conditions to today's conditions, which is what made me consider that being a likely culprit.

Thanks again for the suggestions.

 

[TaperPin]

There’s no way to keep track of a long series of small adjustments over time without a shooting journal.

 

[JPW13]

There’s no way to keep track of a long series of small adjustments over time without a shooting journal.

Agreed. I have one for each of my rifles.

 

[Formidilosus]

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.

100 yard zero does not change due to environmental save wind.

It takes quite a large change in MV due to different temperatures and burn rate to cause a .2 mil shift at 100 yards.

Are you positive that no barrel mirage due to heat played a part in your initial zeroed?

How many rounds were on the barrel when you initially zeroed?

How many are on it now?

Have you cleaned it other wise done anything to the barrel except shoot it?

Have you shot different ammo since the initial zero?

 

[JPW13]

100 yard zero does not change due to environmental save wind.

It takes quite a large change in MV due to different temperatures and burn rate to cause a .2 mil shift at 100 yards.

Are you positive that no barrel mirage due to heat played a part in your initial zeroed?

How many rounds were on the barrel when you initially zeroed?

How many are on it now?

Have you cleaned it other wise done anything to the barrel except shoot it?

Have you shot different ammo since the initial zero?

Are you positive that no barrel mirage due to heat played a part in your initial zeroed? I'm not positive, but feel like I did an ok job of mitigating any mirage. And I've had a lot of success getting on targets at multiple ranges since that zero.

How many rounds were on the barrel when you initially zeroed? Between 100 and 150.

How many are on it now? 400-450.

Have you cleaned it other wise done anything to the barrel except shoot it? First rifle I've just kept shooting it to test for myself after reading this forum and listening to shoot2hunt.

Have you shot different ammo since the initial zero? Yes. I've run 75eldms along with the 77tmks.

 

[Formidilosus]

How many rounds were on the barrel when you initially zeroed? Between 100 and 150.

How many are on it now? 400-450.

There are a bunch of possible small things, but there is a good chance that is it. Barrel “break in” or “settling” tends to be a thing. Somewhere between 80-150 rounds is normal, and it seems that 223’s (at least Tikkas) are on the higher end of that. It also seems the more aggressive a cartridge is, the faster is happens.
I was speaking to a RSer yesterday about this. Groups will vary a bit and mean POI can change until a certain point with barrels. With new 223’s, I zero it and then just shoot the snot out of it for a couple hundred rounds. Then recheck zero and it is not unusual to make a .1 or .2 mil adjustment. After that, it’s extremely rare to have even a .1 mil shift from a true zero.

 

[JPW13]

There are a bunch of possible small things, but there is a good chance that is it. Barrel “break in” or “settling” tends to be a thing. Somewhere between 80-150 rounds is normal, and it seems that 223’s (at least Tikkas) are on the higher end of that. It also seems the more aggressive a cartridge is, the faster is happens.
I was speaking to a RSer yesterday about this. Groups will vary a bit and mean POI can change until a certain point with barrels. With new 223’s, I zero it and then just shoot the snot out of it for a couple hundred rounds. Then recheck zero and it is not unusual to make a .1 or .2 mil adjustment. After that, it’s extremely rare to have even a .1 mil shift from a true zero.

Good to know. Thanks for feedback and for all the testing you do.

 

[Formidilosus]

Good to know. Thanks for feedback and for all the testing you do.

No problem.


The 6cm barrel I have now had a near .2 mil shift somewhere between 60-80 rounds. Adjusted, and has not moved in over 200 rounds. The 22CM had a shift of .1’ish mils around 50 rounds in. We had one of the S2H school tikkas in 223 have a shift at somewhere between 100 and 200 rounds.

It’s a thing until they stabilize.