It seems with the dozen or so thermals I have seen and used all seem to have wandering zero’s
Mostly Pulsar Thermions and all models but others as well.
My IRay Bolt shot a perfect less than half inch group dead on then next shot was 10 inches high and that was the new zero so had to start over?
I never have an issue with normal rifle scopes so this has to be something inherent to the Thermal system.

I don't know. I have owned only two thermal rifle scopes (and a single thermal monocular). The first thermal is a Pulsar Trail XQ30 and there was one occasion when it seemed to lose zero and I missed everything I shot at on that night. To be honest, I'm not sure I didn't screw things up myself pushing buttons but it may have been temperature related on that chilly evening. It seems to have worked fine since then so I assume I inadvertently selected a zeroing profile that hadn't been set up. I have added an AGM Adder TS35-384 to the arsenal recently and only a week ago finished setting up the rifle (new-to-me caliber) and sighting it in. That's admittedly pretty limited experience. I'll have scads of free time on my hands in only months and that experience level is slated for modification!

On the other hand, I know how electronics can be since I've been in the field in various capacities since 1976. Electronics can be quite sensitive to temperature changes and a thermal imaging is all about temperature. Even something as simple as an Eotech can have zero retention problems when temperature changes are extreme. Design engineers generally try to compensate for temperature change in just about any electronic product but effectiveness can vary.

My experience is people sight in on a shooting bench and hunt off a tripod then get on line and say their rifle is not holding zero.

I have owned 4 rifle thermal scopes and tested numerous makes and models for various vendors and manufacturers.

Wandering zeroes are not unique to thermal, as they are present when scopes are defective or improperly designed.

I have seen a model of ATN Thor (zero change ONLY during recording), Flir RS, IRD IR Hunter, and a Steiner RS 35.

ALL were reticle mapping issues, all but the ATN being changes of zero during zoom. These were all consistent and repeatable and most were fixed by manufacturers for the product lines.

Random loss of zero (and random regaining of zero) sounds more like ammo issues, shooter issues, mount tightness issues, etc, which are common with daylight scopes.

Pulsar Trails DID have a heating issue that causes a wandering zero.. They fixed it.

If every thermal scope you have owned can't hold zero, either it is something you are doing, or you have really bad luck.

The chances of owning 12 different thermals with zero issues sounds more like a user issue than a thermal technology issue.

Was this fix accomplished via a software update?

That was years ago. Don't recall what all they did.

Maybe all five of us are just unlucky with with the Thermals we have used over last few years.
The going from bench to tripod can be an issue I agree but that doesn’t explain shooting this group from bench. Then forth shot is 3 inches higher and then next two are off the paper high??
Then re -zeroed and it’s shooting good again for now. So it wasn’t loose mounts, bad ammo etc.
Not that it matters but if you are shooting pigs and larger size targets you may not even notice but we are trying to head shoot coyotes fox and bobcats a lot so if you are off a little its noticeable.
Don’t have any issues with normal rifle scope at all.

Here is 3 shot group after taking two shots to get zero. Next shot was 3 inches higher and next two were off the top of paper target

So it shoots 3 shots just fine and 4th is 3" off. Does the zero stay 3" off?

No next shot was about 6-8 inches higher and I shot again and that one was almost touching…..so I just started over and re-zeroed it again.
So far that has held close enough to hit one bobcat at 75 yds a hog at about 175yds and a lucky 310yd shot on a coyote BUT missed a chip shot at a coyote at 75-80yds but not blaming the scope for that one yet…that was just last night so once I go back to range and see where it’s shooting I will know that answer.
Here is how the rifle shoots with the normal Kahles 624I on it.

NONE of the scopes that I have used or had were afflicted with wandering zeros. Everything was to code, even if the code was wrong.

Surely, you and your buddies never hunted with the dozens scopes, right? You just keep buying and returning them as defective?

However, what you are describing is a classic condition of improper mounting (typically, loose mounting) and it happens with daylight scopes or thermals.

No we have been re-zeroing every week hoping they are still on. Sometimes they are sometimes they are not. Haven’t really thought about it until the drastic change on the latest purchase. We Just assumed that was how they are ,after all they aren’t really that precise anyway as you never really hear about how great my groups are with my new Thermal

Maybe I should be asking what is an acceptable amount of POI shift in a Thermal when adjusting for focus changing powers focusing reticle from one person to another.

I am hoping my sudden drastic change was an anomaly but by next week or so I will know as I plan to shoot one 3 shot group with it for 6-7 days in a row at the 100 yard indoor range to get a baseline for what to expect.

WOW! You are knowing and willingly are hunting with rifles sighted with scopes with wandering zeroes? That is just bonkers.



Unlike daylight scopes, there are no parallax issues. The POI should be the same regardless of the shooter. That is because the crosshairs are located within the image presented to you on a tiny TV screen. Changing focus does not change the relative position of the crosshairs to the rest of the image. Changing zoom doesn't change the position of the reticle to the rest of the image if the reticle is properly mapped. That would be a firmware issue and you would be in the same boat with countless other users and the information would be blowing up on the internet and I don't see that happening and so I don't think it is going to be a reticle mapping issue for all of your units.

Never had mine lose or change zero, even with using the QD Mount every hunt and multiple times during the hunt.

As I said maybe our expectations of precision are different.
This thread has been enlightening and helpful and it could be simple as the fact you can get a very precise zero on a daylight higher magnification scope so it’s easier to hit tiny targets at distance. Thermal scopes maybe are just more difficult to get a very precise zero so that you could say hit a quarter sized target at 100 yds which is what you would expect from an accurate varmint rifle.

I hate to use the term like a normal scope...but the two Pulsars I have do hold min of pig zero. I did notice I had one walk up last year...I rezero'd it and it's held for the last 3-4 times out and I checked it three weeks ago and my 300 Hamr laid 3 down that were all touching. I'd love to tell you that's normal...it'll do it but not every group I shoot, especially w/ the thermal. It will do it with the reg scope on it more regularly.

So...thermals just aren't accurate like a good scope has always been my opinion.

I have run multiple thermals from FLIR and Pulsar. The FLIR had many issues before some of their software updates. The Pulsar I have had a few shifts. The shifts have been pretty small, maybe a few inches, but still killing them. I'll check zero and make some minor adjustments. I have noticed it's hard to shoot a tight group, whether it's from lack being able to see a fine spot for a precise shot or simply it's just not capable of tight groups with a thermal. I have seen some really tight groups being shot with a thermal, but then be off target slightly some when hunting. Overall, I've had really good results with my Pulsar Trail thermal. It's holding zero on my 300 blk out bolt gun currently. I'm about to move it over to my 224 Valkrie again for off season night coyote hunting. (I'm loving the 55 grain Lehigh bullet in the Valkrie!!).

Funny thing about shooting tight groups with a thermal or a red dot sight, people say they aren't accurate or aren't precise, but in reality, they certainly should be and even people like DStroud have posted really good groups from thermal. A lot of it will come down to the end user.

Some thermals may be harder to shoot accurately due to the lack of resolution, lack of magnification, digital zoom, etc., but the zero is absolutely solid and the precision of the rifle doesn't change due to the optic on it, the only change been is that the optic is the user interface.

If I shoot any optic, there is a VERY strong likelihood that I cannot group much smaller than what the crosshair cross, red dot, etc. covers. I used to hunt with a 4 moa red dot on my .45-70 and I would shoot 3-4" groups with my .45-70 and that was sighted at 100 yards. My neighbor could shoot the very same rifle and ammo and cloverleaf the shots on or next to the bullseye. Same gun, same optic, same ammo, same batch of ammo, same target distance, and two very different results. If I put on one of my good rifle scopes, I could shoot the same groups as my partner (and did). The bottom line here is that the optic wasn't at issue, but the shooter's ability to adapt to it.

The same goes for thermals. I can shoot better groups on thermals of comparable magnification and resolution that have fine crosshairs than some of these thick lined reticles. Why? The trick is really being able to see well enough to actually hold in the exact same place for each shot. Lots of people have trouble doing unless the image and crosshairs are well refined. It is just harder to shoot tight groups with some thermals, but that doesn't mean the thermal isn't up to the job.

I've had minor POI shift (1"-1.5") due to a drastic change in temp (30 to 90 degrees) with both Pulsar Trail and Thermion but after months of use my Burris BTS-50 is still dead on. The issue with the early Trails was a plastic internal chassis that moved internal components when it got hot. I only turn mine on after I spot game and turn it off after shooting so I've never experienced this POI shift. The newer Trails have a magnesium chassis and aren't supposed to suffer from this issue.

I just got a new Thermion 2 XQ50 Pro and have only hunted two nights with it, so I can't say how it will hold zero. It's sure a nice scope though, I actually like it better than the more expensive XP50 Pro.

Overall I haven't seen much of an issue with POI shift and I've had the following thermal scopes and still have the ones with a *:

FLIR PTS536
Trail XQ50 (original model) *
Trail XQ50 LRF
Thermion XM38
Thermion XQ50
Thermion 2 XQ50 *
Burris BTS-50 *
Thermion 2 XP50 Pro *
Thermion 2 XQ50 Pro *

A 60 degree change in temperature could certainly result in a similar change in POI regardless of the optic used. That is because it would not be an optic issue, but a powder temperature issue.

I feel some of the scopes move. When I had my pulsar I feel I had to check it more. It was for sure not as hood with their crappy factory mount. The Bobro improved it

My current Bering seems to hold still but I haven't put it on paper lately

No such thing as coincidence.

You've had this issue with a dozen thermals. Different guns/mounts, or the same rail?

I've never shot an ATN that would accept or hold a zero without issue. In one instance, the wobble traced to the QD mount. The cross rail was too narrow and didn't fit snugly between the guns' pic rail. That unit would also randomly reset to factory zero. In each system, it was the electronics or programming screwing up.

Had an odd issue with my Pulsar the other day. Zeroed gun no. 5A @ 100 with 168TSXs. The 180 subs hit 4 mils low at 100. So I moved the 5B zero down 4 and assumed I could just jump between rounds by flicking between 50/100 yard settings. Nuuupe. Whatever I (actually) did completely screwed up both zeros.

I sighted both of mine in about 10 years ago and haven't touched it since. IR Hunter Mark 2 and Pulsar XD50A. Neither one has ever had an issue.

Since I opened the worm box I guess I need to make an effort to see what I can learn from all the input above.
Would have already checked my zero for 3 days except for the inclement weather my indoor range has been closed since Sunday.

I plan to shoot each day a 3 shot spaced out group with no changes from when it was zeroed last Friday night.
So if it’s off next time it will get no adjustments to rectify just keep rolling until I have to hunt with it again or get tired of checking perfection.
Fortunately the rifle is a very good shooting platform and it’s my hand loads so no change in lot number etc. It’s indoors so no wind or temperature changes.
Should shed some light hopefully.

I will say that since the first post I have spoken with several knowledgeable hunters that hunt pigs/ varmints maybe not every day but at least two days a week all year long and have owned over (one way over) 3 Thermals on multiple platforms and the consensus I get is they hold zero pretty well generally speaking but when addressing the precise placement of shots on a target…..well let’s just say they felt like if the pig is big enough they were confident
One person the one with the most experience says he has videos of known sighted in rifles that the video shows the crosshairs perfectly placed with the shot missing and when checked rifle was still GTG. My varmint hunting partner has complained of this last two weeks….. I just think he is whiner but he insists he has the video to show me.
He is trying to head shoot so it maybe just is how precise can you hold like mentioned above?
Anyway good info above from all and Thanks for the responses.

Never had an issue with thermal loosing zero but I always confirm before hunting.

They work like a raster scan (normal) TV. Sensor is scanned, software then converts (digital zoom) to display (scanned again) and the reticle tossed into the display. Any TIMING error and zero is 'lost'. Add the size of the sensor elements and display pixels, very easy to get 'blur' - reticle in the wrong pixel. Timing is highly influenced by temp change - cheap crystal! Used to design cooled FLIRs.