Scope temperature shift fixes

[ocedummy]

About four or five years ago I went to the FT Nationals at Phoenix. I was using a Sightron SIII 10-50 at that time and when HFT started I was doing well, after 3 lanes I had only missed one. I could taste the victory that was coming, then the next lane I missed 2, then 2 lanes where I got 1 or 2, then a 2 lanes where I got zero! I tried to stay out of the sun but was unsuccessful. Previously my matches were in the woods with very little temperature change, That desert sun was brutal. Anyway, after the zero lanes I panicked but noticed a weed moved about 3 inches high and 1 inch left of the edge of the faceplate on one of the long shots, I couldn't even hit the faceplates on long shots. Tried to guess the new holdovers but it sucked and it happened the next day, I came in last, no more sun shoots for me with the Sightron. When I got home, 1450 miles, I took two of my FT guns with scopes and zeroed them at 70 degrees in an air-conditioned room shooting thru the window to 50 yards. Then outside for over an hour in bright sun and 93 degrees air temperature both scope temps were about 105 degrees, shot them both at 50 yards and the Sightron shifted big time again, but the other, a Millette 4-16 Tactical hardly shifted . Then I got sick for 3 years so no shooting, I just got my Red Wolf back from AOA for a reseal and I put the Millette back on and it ranges well and the Sightron can fool me because it doesn't snap into focus like the Millette, it is semi-clear and then gets real clear, you have to pay attention. The SIII is so clear that if the target is between 20 and 32 yards I wouldn't even refocus to hit the kill zone. Also the Sightron, since it is clearer, you can see the kill zones better and if you miss, you can see the faceplate hit easier. Another time my partner couldn't see the kill zone, small and lots of misses on the edge, when it was my turn, the Sightron could see the edges of the killzone hole. And if shooting benchrest, the Sightron is the hot ticket.

 

[MysticalDragon]

About four or five years ago I went to the FT Nationals at Phoenix. I was using a Sightron SIII 10-50 at that time and when HFT started I was doing well, after 3 lanes I had only missed one. I could taste the victory that was coming, then the next lane I missed 2, then 2 lanes where I got 1 or 2, then a 2 lanes where I got zero! I tried to stay out of the sun but was unsuccessful. Previously my matches were in the woods with very little temperature change, That desert sun was brutal. Anyway, after the zero lanes I panicked but noticed a weed moved about 3 inches high and 1 inch left of the edge of the faceplate on one of the long shots, I couldn't even hit the faceplates on long shots. Tried to guess the new holdovers but it sucked and it happened the next day, I came in last, no more sun shoots for me with the Sightron. When I got home, 1450 miles, I took two of my FT guns with scopes and zeroed them at 70 degrees in an air-conditioned room shooting thru the window to 50 yards. Then outside for over an hour in bright sun and 93 degrees air temperature both scope temps were about 105 degrees, shot them both at 50 yards and the Sightron shifted big time again, but the other, a Millette 4-16 Tactical hardly shifted . Then I got sick for 3 years so no shooting, I just got my Red Wolf back from AOA for a reseal and I put the Millette back on and it ranges well and the Sightron can fool me because it doesn't snap into focus like the Millette, it is semi-clear and then gets real clear, you have to pay attention. The SIII is so clear that if the target is between 20 and 32 yards I wouldn't even refocus to hit the kill zone. Also the Sightron, since it is clearer, you can see the kill zones better and if you miss, you can see the faceplate hit easier. Another time my partner couldn't see the kill zone, small and lots of misses on the edge, when it was my turn, the Sightron could see the edges of the killzone hole. And if shooting benchrest, the Sightron is the hot ticket.

Thats odd that you say the sightron doesnt snap into focus as thats one of the things that everyone raves about the sightron with.

 

[steve123]

About four or five years ago I went to the FT Nationals at Phoenix. I was using a Sightron SIII 10-50 at that time and when HFT started I was doing well, after 3 lanes I had only missed one. I could taste the victory that was coming, then the next lane I missed 2, then 2 lanes where I got 1 or 2, then a 2 lanes where I got zero! I tried to stay out of the sun but was unsuccessful. Previously my matches were in the woods with very little temperature change, That desert sun was brutal. Anyway, after the zero lanes I panicked but noticed a weed moved about 3 inches high and 1 inch left of the edge of the faceplate on one of the long shots, I couldn't even hit the faceplates on long shots. Tried to guess the new holdovers but it sucked and it happened the next day, I came in last, no more sun shoots for me with the Sightron. When I got home, 1450 miles, I took two of my FT guns with scopes and zeroed them at 70 degrees in an air-conditioned room shooting thru the window to 50 yards. Then outside for over an hour in bright sun and 93 degrees air temperature both scope temps were about 105 degrees, shot them both at 50 yards and the Sightron shifted big time again, but the other, a Millette 4-16 Tactical hardly shifted . Then I got sick for 3 years so no shooting, I just got my Red Wolf back from AOA for a reseal and I put the Millette back on and it ranges well and the Sightron can fool me because it doesn't snap into focus like the Millette, it is semi-clear and then gets real clear, you have to pay attention. The SIII is so clear that if the target is between 20 and 32 yards I wouldn't even refocus to hit the kill zone. Also the Sightron, since it is clearer, you can see the kill zones better and if you miss, you can see the faceplate hit easier. Another time my partner couldn't see the kill zone, small and lots of misses on the edge, when it was my turn, the Sightron could see the edges of the killzone hole. And if shooting benchrest, the Sightron is the hot ticket.

Send it back for repair or replacement.

One time I took the chance at a state match with some older super cheap aluminum rings I had laying around that I installed on my USFT. I had a POI shift which took a while to deduce where I was missing then started compensating but the same thing, another POI shift, happened later in the match.
I used Steel Nightforce rings after that and the POI shift didn't happen again.

Starting early last year and ending a few months ago I was trying another brand of scope than I had been previously using on my Thomas. During that time I had ordered another batch of pellets. Long story short I thought I had a bad batch of pellets because of occasional flyers but recently when I put my new Athlon Ares ETR 15-60 on my gun the flyers stopped.
So it must have been the other scope. The thing was that the flyers were so "occasional" that I couldn't draw 'the" correlation. However the last match I used the other scope was the worst. Heck even my super good shooting daughter was missing easy targets.
I've owned lots of scopes and never thought it could have been the scope based on the way the symptoms played out which were just enough to miss a KZ and only one in 30 to 40 shots.

 

[Arzrover]

Poi shift and ranging error are not the same thing. Either will result in a miss but on the scopes I've had that shifted, it was never just vertical. Ranging error will only result in a vertical error unless combined with wind estimation error.
The worst poi shifter I've had was a Sightron SIII. You could put a temp tape on it to know when it's getting close... it's pretty consistent, depending on mounts and mount torque. The depth of field seems small to me so I don't understand the statement about shooting from 25 to 32 yds without refocusing. Wouldn't be able to see the kz at 32 yds if scope was on 25 on the ones I've used.
The thing about shooting in AZ is that we can get 50 deg temp swings and 40+ deg temp swings are fairly common. Sight in at 35 deg, then temp rises to 75 or more and having your rifle in the sun even briefly can push the scope to over 100 deg. That's a tough scenario for dissimilar metals like steel and aluminum.
Bob

 

[Greg5850]

Some further food for thought. Since almost all guns shoot a bit low when very cold and a bit high when very hot (Cold air heavier, hot air thinner)if your scope ranges long when cold and short when hot,the system is somewhat self correcting. If your scope ranges short when cold and vice versa it will compound the issue. Many popular scopes do this.

I had a big Nikko ( early Sightron) on my gun in Tennessee when the am temp was below 40. I had to add 12 clicks to everything. As the day warmed I added less and less clicks till I was back to zero

Figure out at what temps ( high and low) that your scope moves, and how much it moves. Then figure out how much POI shift you get as the temp shifts.
Use the combined information to determine your aim point. Absolutely knowing the distance will not guarantee accurate shots.

 

[cavedweller]

Let me apologize. I take "sighter" shots when I am shooting at ~93 yards.

From 10 to 63 yards, I know my hold overs and since I know my velocity within 5fps or better for ~28 shots...

Well, I think I might do OK in FT. My kill zone is .33" and my PBR is ~22-44 yards.

Until recently, all my shooting/pesting (last 6 years) was much lower power. Not exactly 12fpe, but close shooting out to 63 yards. So, I don't see a huge transition for me shooting 12fpe. I only recently purchased a laser range finder and found that my eyeball estimates were very close. Even the range finder is +/-1 yard.

I completely understand about that first shot. That is why I will never own another regulated gun. I would rather have a sweet spot that I can count on than depend on a regulator that WILL fail.

Yes, we will have to agree to disagree.

@BackStop - come visit us in pensacola Fl 1st Saturday of the month at Santa Rosa shooting center and we will introduce you to field target

 

[Ezana4CE]

Simple towel or sunshade of some kind over the scope when not in use.

Or if you have the coins get the March highmaster series scopes.

@qball Do the Highmasters withstand heat better than most other scopes?

 

[JEFFPPC]

As a longtime PB benchrest shooter having used various brands of scopes including 2 Sightron SVEDs I have never heard of such a thing. As the temperature goes up your velocity can go up out of the node and cause you to shoot higher. Bright sun can. But most often the cause is a boil effect or parallex running straight vertical. Not saying I m the sharpest knife in the drawer and living in the NE might have something to do with this but in all the reading, forum discussions etc. I have never heard this mentioned. Never to old to learn, I am following this with interest..Does this appear in both springers and pcps.

 

[JEFFPPC]

Another question to Springer shooters In you shot 1 long string say 50 or 100 pellets over a chronograph as the spring is exercised over that 50 or 100 shot string does the velocity trend either up or down?

 

[qball]

@qball Do the Highmasters withstand heat better than most other scopes?

Supposedly! Couldn’t justify the coins to try one but March is OG milspec and high master glass composition and construction supposedly are not affected by heat.

Cheap way to prevent temp shift is simply avoid direct sunlight exposure, a cheap white towel over the scope would work.

 

[scotton]

As a longtime PB benchrest shooter having used various brands of scopes including 2 Sightron SVEDs I have never heard of such a thing. As the temperature goes up your velocity can go up out of the node and cause you to shoot higher. Bright sun can. But most often the cause is a boil effect or parallex running straight vertical. Not saying I m the sharpest knife in the drawer and living in the NE might have something to do with this but in all the reading, forum discussions etc. I have never heard this mentioned. Never to old to learn, I am following this with interest..Does this appear in both springers and pcps.

Bear in mind we are talking about two different things here. The original post was about using the parallax wheel to range find and issues that heat can cause to the ability to rangefind with parallax focus. As a bench rest shooter, you will not have noticed this because you are always shooting a fixed, known distance.
Some other people are conflating this with temperature related POI or POA shifts from the scope. I have not experienced this as far as I know, so I don't have an opinion on this. Now we are apparently talking about velocity shifts due to temperature changes.

 

[scotton]

Another question to Springer shooters In you shot 1 long string say 50 or 100 pellets over a chronograph as the spring is exercised over that 50 or 100 shot string does the velocity trend either up or down?

After the first couple of shots, velocity should be stable for the duration of the shooting session if the ambient temperature is stable. The main factor that would influence the velocity over a large number of shots would be the ambient temperature. Springers generally react opposite to PCPs. When springers get hotter, they get slower. This is because the piston seal and guides will swell when hot, causing more friction and slowing down the pellet velocity. Some are worse than others, depending on the design of the gun and the materials used for the piston seal and guides.
For example, in my HW97 I have two piston seals: cold and hot. The hot seal gives me about 11.8 foot pounds at 80 degrees and 11.5 foot pounds at 100 degrees. If I use this seal when it's 35 degrees, it would be 13 foot pounds. So when temps drop below 70 degrees for the year, I switch to the cold seal.

 

[beerthief]

Me and my guns live in a temperature and humidity controlled house . (HVAC) the house and basement remains the same year around . just outside my basement door is my shooting stand . i allow at least 10 minutes for any gun to acclimate to the outside . (but i am retired so time does not matter to me )

 

[JEFFPPC]

After the first couple of shots, velocity should be stable for the duration of the shooting session if the ambient temperature is stable. The main factor that would influence the velocity over a large number of shots would be the ambient temperature. Springers generally react opposite to PCPs. When springers get hotter, they get slower. This is because the piston seal and guides will swell when hot, causing more friction and slowing down the pellet velocity. Some are worse than others, depending on the design of the gun and the materials used for the piston seal and guides.
For example, in my HW97 I have two piston seals: cold and hot. The hot seal gives me about 11.8 foot pounds at 80 degrees and 11.5 foot pounds at 100 degrees. If I use this seal when it's 35 degrees, it would be 13 foot pounds. So when temps drop below 70 degrees for the year, I switch to the cold seal.

Thanks, I said hotter but colder could for the same thing, putting you out
of node/tune by altering velocity sufficiently

 

[JEFFPPC]

Bear in mind we are talking about two different things here. The original post was about using the parallax wheel to range find and issues that heat can cause to the ability to rangefind with parallax focus. As a bench rest shooter, you will not have noticed this because you are always shooting a fixed, known distance.
Some other people are conflating this with temperature related POI or POA shifts from the scope. I have not experienced this as far as I know, so I don't have an opinion on this. Now we are apparently talking about velocity shifts due to temperature changes.

You are right, but also incorrect. You do set your, parallex for a given range but that does not eliminate the effects of boiling mirage. I refer to mirage bubbling straight up as boiling. It can be confusing. If it's slight you might dial some of it out but if it's bad you can not. It's interesting Sightron was brought into this as the SVED scope with it's 4to1 ratio on the parallex knob allows you to stop at the precise spot to eliminate the movement you are viewing much more precise than other scopes. I spoke with a long time top level PB bench shooter this morning and asked him his thought on the issue of the scope tube being affected by heat, I received a very strange look. I think you guys are barking up the wrong tree. Until you understand mirage you will be confused. And yes mirage can also happen in cold weather.

 

[scotton]

You are right, but also incorrect. You do set your, parallex for a given range but that does not eliminate the effects of boiling mirage. I refer to mirage bubbling straight up as boiling. It can be confusing. If it's slight you might dial some of it out but if it's bad you can not. It's interesting Sightron was brought into this as the SVED scope with it's 4to1 ratio on the parallex knob allows you to stop at the precise spot to eliminate the movement you are viewing much more precise than other scopes. I spoke with a long time top level PB bench shooter this morning and asked him his thought on the issue of the scope tube being affected by heat, I received a very strange look. I think you guys are barking up the wrong tree. Until you understand mirage you will be confused. And yes mirage can also happen in cold weather.

I understand what you are saying. I'm fairly sure all field target shooters have experienced mirage, and it definitely can affect the ability to range find with a scope. But that is not the tree that we are barking up with this thread. Outside of a couple of sidetracks, we are discussing how temperature differences affect the ability to range find with the scope. This is independent of shooting, has nothing to do with POI or POA, the scope doesn't even need to be mounted to a gun for this issue. It's about the scope telling you that a target is 50 yards away when it's actually 46 yards away because today is 30 degrees hotter (or colder) than the day when you figured out what 50 yards through the scope was supposed to look like. This is a problem unique to field target shooting because we are the only shooting sport that use our scopes to range find as well as to shoot. I'm not saying we don't have to worry about mirage or POI issues or pellet velocity. We do have to worry about all of that stuff. We just also have to worry about how the scope works as a rangefinder at different temperatures.

If you start a thread about dealing with mirage, I would be very excited to read your thoughts. I know that I have a lot to learn on that subject.

 

[cavedweller]

As a longtime PB benchrest shooter having used various brands of scopes including 2 Sightron SVEDs I have never heard of such a thing. As the temperature goes up your velocity can go up out of the node and cause you to shoot higher. Bright sun can. But most often the cause is a boil effect or parallex running straight vertical. Not saying I m the sharpest knife in the drawer and living in the NE might have something to do with this but in all the reading, forum discussions etc. I have never heard this mentioned. Never to old to learn, I am following this with interest..Does this appear in both springers and pcps.

Temperature affects the way field target shooters use a scopes parallax adjustment to determine distance - the air volume in the scope tube IS affected by pressure changes from temperature changes so the scope doesn’t focus the same way when adjusting for parallax

 

[JEFFPPC]

Well live and learn. No field target experience here, just a good Electronic range finder for groundhog hunting. No mirage that is an issue of its own . No easy answers Maybe start that thread some day I am bored.

 

[Arzrover]

The OP asked about ranging errors AND poi shifting with temperature change.

Not many bench shooters will have their equipment in the sun and since you can shoot sighters, not much of an issue anyway.

Mirage can be a problem but won't usually result in a repeatable poi shift... it just creates a difficulty deciding where to hold.

Afik, ALL scopes change some in ranging with changes in temp. Some are just worse than others. NOT ALL scopes have poi shift with changing temps... THIS is the factor I am concerned about.

Having competed in more than a couple of FT matches, can't even have an idea how many fellow competitors have complained about poi changes during the match.

So... I keep my rifle in a case and out of the sun between lanes and all other times when not shooting... even though my beloved Elite 4200 hasn't shifted yet that I know of. I admire the nice, convenient carriers I've seen, but try to limit sun and dust exposure all I can.

Bob

 

[cavedweller]

Well live and learn. No field target experience here, just a good Electronic range finder for groundhog hunting. No mirage that is an issue of its own . No easy answers Maybe start that thread some day I am bored.

It is interesting how HFT evolved over the years - the use of parallax adjustments to a scope to determine distance, was “according to several” high end scope manufacturers - NOT intended or recommended.