Has anybody had any trouble with this scope losing zero when exposed to single digit temps? I have had this happen twice now over the last month. The first time it happened i checked and retightened all the screws from the bases all the way to the ring caps. After doing this i tested in 20 degree temps with no issues. Last night however it got back down in the single digits and after hunting i found that the impact had shifted 8 inches lower and 4 inches to the right at 200yds. I checked the zero before going out that night and everything was fine. Upon finding out the poi had moved i shot the rifle both warm/cold and the poi remained the same. I then checked that all the mounting hardware was tight and found nothing out of the ordinary. Called Pulsar this morning and they recommended trying reverting everything back factory default settings and rezeroing before i resort to sending it in. Upon doing that and rezeroing, the poi has not shifted when i cycled the gun from cold to warm multiple times this morning. Im hoping this solved the problem somehow. Just looking for some opinions before i end up having to send the scope back in to Pulsar as its been hard to trust the scope for accuracy as of late when it gets cold.
Night Vision Pulsar Thermion 2 XG50 losing zero
- Thread starter bd05320
- Start date
I have hunted down to -20 with both a Pulsar Thermion XL50 and XG50. I am going from a warm truck to these temps and staying on stand for 30+ minutes, back in the truck, and back out etc. I didn't have any POI shifts. The only odd thing is the internal battery showed yellow when it was out for long periods of time. Scope still operated fine, but just FYI.
Recording Zero: Write down your zero coordinates and for which profile/gun it is for and store the information on your phone. This way if your zero moves, you can go in and verify your coordinates haven't changed.
Broken Scope Seal: Put the gun and scope on a tripod or whatever you have that is solid, and lock everything tight so there is no wiggle. Press any of the 3 buttons on the top. If you can see the crosshairs move, and nothing else is really moving, then you may have broken the seal between the tube assembly and the eyepiece. If you can flex those two pieces at all, you have an issue, and it needs to go in.
ADM Mounts: If using ADM mounts, I have heard of people over-torquing their mounting screws. Start on the bottom and use 20-25 lbs and then repeat on the top. Tighter isn't better. I have seen over-torqued screws cause a variety of issues.
Other Tips:
Recording Zero: Write down your zero coordinates and for which profile/gun it is for and store the information on your phone. This way if your zero moves, you can go in and verify your coordinates haven't changed.
Broken Scope Seal: Put the gun and scope on a tripod or whatever you have that is solid, and lock everything tight so there is no wiggle. Press any of the 3 buttons on the top. If you can see the crosshairs move, and nothing else is really moving, then you may have broken the seal between the tube assembly and the eyepiece. If you can flex those two pieces at all, you have an issue, and it needs to go in.
ADM Mounts: If using ADM mounts, I have heard of people over-torquing their mounting screws. Start on the bottom and use 20-25 lbs and then repeat on the top. Tighter isn't better. I have seen over-torqued screws cause a variety of issues.
Other Tips:
- Make sure you are always zeroing off the same setup at the exact same distance. Not using bags in one situation and tripod in another, etc.
- Many powders are very temp sensitive. It shouldn't be as drastic as mentioned, but it is the reason I shoot as temp insensitive as I can find.
- Make sure you have a small aimpoint for your thermal target. Don't shoot at a huge blob. Use a thermal target that can give you a small aimpoint. I will use hvac tape, and make a corner with it vs shooting at a large blooming heat source.
- Many people don't realize the height over bore is typically higher for a thermal than for glass scope. They zero their thermal exactly the same and end up shooting too high in the sweet spot of their range trying to extend their PBR too far. Measure your height over mid-line of your bore to your ballistic tables and adjust accordingly. I realize this issue isn't about a POI shift, but many people blame a POI shift for misses, so including it.
- Have someone else try. Story below.
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Thank you for the things to try. I just got done checking the buttons and scope housing and nothing seems to be moving. Zero has been holding. Hopefully it may have just been a software glitch and the reset that Pulsar said to do remedied the situation. When the poi shifted i tested the ammunition cold and warm before making any adjustments and it was still grouping well within 1 MOA at 200yds, just the group was off center. I double checked the coordinates as well when i had the problem and nothing had changed. I have cycled the gun from cold to warm and shot it both ways and it seems to be shooting back normal after moving the coordinates to get the group back centered. As for the mount i am using a MPA BA mount and everything is torqued down to their specifications. I have been unable to replicate the problem since. I had thought about the powder being too cold and something being unstable, but since the consistency had remained I've kind of ruled that out. The only other thing that has puzzled me is if somehow the cold caused the mount to become loose and it shifted. However the last time it did it, I checked the torque while everything was still cold and nothing was out of place. The scope itself also did not slip in the rings or anything because i have a witness mark on it in case that were to happen.
Sounds like you have done everything you can, and it has not reoccurred.
Hopefully, it was a fluke. I forgot to ask if you are shooting suppressed. A loose suppressor or a baffle strike may be something to watch out for as well.
This comment is not meant for bd05320 because this issue doesn't typically happen with tube scopes like the Pulsar Thermions. Many compact thermals are blamed for POI shift when put on bolt guns. People will literally hang them on the last rail slot with all their weight hanging off the back of the gun and wonder why they are getting vertical shifting in their POI. You need to get the weight balanced on the rail and this will vary depending on the gun/scope. Scoot the scope forward and if the POI shift stops happening you found the issue. Then you have to determine the best option to get it comfortable on that gun. When I was shooting more compact thermals, I used a LaRue LT101 riser to get my scopes far enough back to work on bolt action rifles in a chassis.
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