At what temp does your scope shift ?

[travelbike]

Been noticing changes in range finding esp in hot weather. Never really occurred to me that there is such a phenomenon until I read an article in hardairmag a few months back. When the gun would suddenly shoot high or low, my initial reaction was to blame the gun or the scope not holding true. Temperature was the least of my suspect. 

Decided to wake up early one day when the temp was in the low 60s and the day would heat up to high 90s. I'm lucky to have targets in 5 yard increments to 55 yards.

 

I think I marked my scope wheel back last fall when it was colder (not sure at what temp though). Started to range find the 55 yard mark before the sun was fully out with temp at the low 60s. It was spot on. I then continued to range find as the day got warmer. At bet 68 and 70F, the shift occurred. The scope shifted about 5 yards more. The 55 yard was now focusing sharp at about 60 yards. It stayed this way to the high 90s.

Tried to google topics on scope shift but not too many I can find. But in the last video posted by AEAC titled "Pyramid Air Cup the Movie", an interview with the WFTF champion Jack Harris was a revelation. He has 3 sets of scope wheel marking for 3 specific temperature ranges (48F and below, 48F to 77F and 77F above). The interview is about 1 hour 10minutes into the video.

I use the inexpensive Tac Vector 10-40 scope. For temp reading I use an aquarium stick on thermometer. 

From the video interview, it seems a digital thermometer is the way to go for a more accurate reading. 

So if you have observed temperature scope shift, maybe share your experience and how you resolved it to shoot better.

My game plan now is first get a digital thermometer. Then observe at exactly temps the shift would occur with the digital reading. Will there be one or 2 shift points ? Then verify if I have to make a different holdover cheat sheet for the different shift points. Plan on shooting a pellet drop profile at 5 yard increments.

Does it sound like a sensible game plan ?

 

[Michael]

I'm curious to read the replies, I "Subscribed" to this topic. Thanks 

 

[ranedouglas]

... ghost in the machine....GHOST in the SCOPE ?!?!? .... i'd like to see what's going on here , too..... i just got off the phone with the former owner of sun optics usa , and he was explaining that some of these optics factories over there in china have no clean room (dust-free, air filtered environment for the assembly of optics and filling of nitrogen inside the tube, and sometimes high-quality lenses made in clean rooms).... i was mentioning about the cheaper single focal plane scopes crosman had offered... it's pretty damn hot here in texas lately , so much so that if you leave your break barrel spring / piston air rifle out in the shed the dang lubes melt or migrate to one end ... twang returns... it's a whole different shot cycle. i inverted my .22 rws mdel 94 for the next night and rectified the texas meltdown... my piston-based air rifles , which have a lot of moving parts in the lock-time or shot cycle , act differently after the first 5-10 shots - especially if it's cold outside. they need to warm up - unless you have a well-tuned r9 or a good english or german one. even my np2 gas ram rifles act MUCH better in 50-60 degree weather.... i noticed an 'optimum' temp for whatever they load inside these mass-produced , inexpensive np2 struts or rams - 820 fps with 14.3 grainers on those days , then back to 780-790 when it gets warmer .. hey , travelbike , i'm having trouble digesting your paper of shots at different distances - but youre not having a windage problem , rt ? it's an elevation discrepancy , rt ? .......can you share what make and model of .177 air rifle you have that scope on ? i would hope that these more expensive (regulated) pcp air rifles would soar above any strange ufo temperature problems , but idk.. - paul.

 

[fishinwrench]

I don't know if it is "scope shift" or what it is, but every gun I have (2 break barrels, 2 pumpers, and 2 PCP's) all shoot the tightest groups when it is between 65-75°

Sighting in any of those guns in the morning or evening when the temp is rapidly climbing/falling will drive you absolutely batpoop crazy, with a flyer about every 4th or 5th shot.

 

[ranedouglas]

... ive been in a situation where smoke in the bore caused flyers....those dang mendoza break barrels - that were made to diesel , even if i didnt put 'combustable fuels' in those , they would smoke , and if i didnt blow out the smoke - it'd cause flyers.... thought i was just in 'ufo' lobotomy land , but a guy in far south texas i had done some trading with , caro , told me he was having the same phenomenon ... we were getting those mendoza rifles from glenn seiter at umarex refurb and return and used demos backstock [ man , those were the good ol days , man !! glenn was soooo coool - he'd send me parts if an "R" stamped gun wasnt acting right , or do whatever to make sure we didnt have to send one back to him...diana, walther falcon hunters (later the hatsan 125), cometas , noricas , mendozas (were badged hammerlis then).....25 cal model 48 black pros , etc ] ... that caro fella was a rancher down there. trapped wild hogs in those cage traps , and cold lead massaged those big bastards right behind the ear with the .22 webley jaguars i was wholesaling , which was a dressed up hatsan model 60 - before quattro days , but they shot 770-800 fps with 14.3's ... like a .22 version of the daisy powerline 1000 rifles made in turkey (probably the most powerful airgun daisy ever put their name on..... ....but yeah , travelbike - if you have a regulated pcp air rifle or something like a theoben bottle gun , or bsa super ten (r10 now) , then i'm getting outta this haunted scope house... - paul.

 

[azuaro]

Hello Members:



This is more my experience than a direct response to the topic ,but I may answer some part of the issues presented….I'm going long, so bring your cup of coffee and a comfortable chair...I don't participate in this forum but an active member and a friend asked me to contribute my experience.



First and foremost: I am assuming that the shooter has verified that the “Shift” in POI is actually the scope and not the velocity of the gun which also varies with temperature…If the issue is the parallax shifting, then the problem is definitely the scope and there isn't much you can do about it.



A riflescope has 3 main areas that can be affected by temperature: Windage, Elevation and Parallax…Focus can in theory vary as the glass is mounted over metal that expands and contracts with temperature, but I've never seen a riflescope with focusing issues derived from shifts in temperature.

PARALLAX is the most frequently problem encountered.



SOME (not all) scopes shift with temperature because of the different materials used: Aluminum, Brass, Stainless Steel, etc.

All of these metals have a different Thermal Expansion Coefficient but there is also another factor: TOLERANCES between components of the same metal and in between different metals…Brass is sturdy and widely used in turret mechanisms, it also is easy to machine...But other metals like Stainless Steel or alloys high in Nickel have a much better thermal coefficient…



Scopes are generally assembled using an aluminum tube that has windage and elevation turrets (mechanisms), Brass is the preferred material for the internal mechanisms (good scopes) because it is sturdy and easy to machine, Stainless and other metals/materials are also used. There should be specific tight tolerances in between the metal components considering their VERY DIFFERENT Thermal Expansion Coefficients (TEC), but unfortunately scopes are hand assembled and not all operators are as precise doing their work and not all companies use controlled environment assembly rooms….



We all have heard: “Trash in-Trash Out” and this say applies to scope assembly…If the company does not use a controlled environment in their assembly rooms then the tolerances set during assembling are not going to be precise (trash in)…Assembly deficiencies as mentioned is why we find scopes (same brand and model and same internals) that are very precise and some others that easily vary with a slight change in temperature…Add assembly precision and other deficiencies to aggravate the problem…



We are in the aerospace business (lab) and in this industry thermal issues are strictly monitored and tested continuously…If you ask me, INVAR is one of my preferred metals as it is used in all airplane and aerospace instrumentation, but it would be very costly and not justifiable for using it in scope mechanisms…Other metals rich in NICKEL and some others in CHROME are also very good for their low TEC, but this is another topic...



The initial post of this thread asks about “HOW HAS THIS TEMPERATURE ISSUE BEEN FIXED…”

There is nothing the shooter or end user can do about temperature derived scope issues…Getting another scope is the answer…

Of course that you can minimize the problem by shielding your scope (insulation or covering your scope while not in use) or you can make tables and actualize them based on real variations experienced…I don’t do tables, my scopes are either very precise or are not part of my equipment.



Back in 2010-2012 I bought a Schmidt and Bender 10-50 x 56 FT Scope, It was announced in Europe and the US and I was on top of the waiting list for 2+ years…At the time I got it its price in the US was $3,400.00 and it was supposedly the best of the best Field Target scope ever made with specs defined by the best European FT champions....It was widely used in Europe and it came with a 30 mm tube and side adjusting parallax wheel…

ALL of these S&B FT scopes were plagued with issues in the materials/tolerances that affected the Parallax mechanism drastically, in my scope the 35 yard mark in the parallax wheel varied from 28 to 35 meters depending on temperature (25% error)…After almost 16 months of unsuccessful back and forth with S&B, I ended up selling this scope on eBay for $1,100 to somebody who didn’t use the Parallax wheel for range finding and wanted the scope exclusively for Benchrest shooting…



S&B discontinued this FT model and replaced it after 5-6 years with the exceptional 10-50 x 56 PMII with a 34 mm tube and 10 Meter parallax...I use one of these scopes and have two 5-25 x 56 PMII's...All three are exceptional scopes with zero issues at 24-26 F in Montana and at 90+ F temps in Arizona but so are my Leupold Comp 40 X and my Sightron 10-50 x 56 MOA...In the past I had a Leupold VXIII that slightly changed its POI with temp, I called Leupold and they sent me a brand new one overnight before I sent mine back...How is that for an extraordinary customer oriented company?



So if the temperature is affecting your POI, get another scope...If it is affecting the parallax, then it is not an issue unless you are using the scope for FT shooting where you use the parallax for range finding distances...It is important to differentiate in between a scope parallax error and a situation where MIRAGE is somewhat compensated using the parallax wheel, this Mirage adjustment can be interpreted as the parallax wheel not marking the correct distance (when using it for range finding). 



Regards for all members,



AZ

 

[nomojo65]

IMO only!, simply buy scopes made and assembled by L.O.W.!

 

[lenweber2]

Temp has less affect than Sun on the top of scope and barrel. Heating dramatically on one side or and top.

 

[shutik]

Travelbike,

I think you are on the right course.

I've been shooting FT for 2 years now and had number of scopes. They all shift ranging when temperature changes.

1. Having temperature tape is good enough IMO, as long as it covers temperature ranges where shifts occur. I've also seen people carry digital laser thermometer and check scope temperature.

2. You can have 3 color lines for reading distance like Jack has in the video. Most scopes will range shorter when cold and longer when hot.

You can have adjustable pointer that you move with temperature.

I'll try to take some pictures and post to them later of this set up.

It takes about a year of regular shooting with same scope to figure out ins and outs of it. Knowing your scope is more important than knowing your rifle in FT.

Happy shooting, Vasyl.

 

[chasdicapua]

Thanks AZ for taking the time to pass on that info. I use a Sightron Slll for FT shooting. I notice some range finding differences between say 65 and 85 degrees. I think I'm going to do what Jack from England does and make different range cards. I do 90% of my FT shooting at temps between 65 and 85 degrees. Although it can be much colder at our March and April matches! I'll have to see how many I need (2 or 3) and at what temperature intervals. Sounds like a fun project!

Chas

 

[boscoebrea]

Interesting,what's said,"it's all in the details"....having ADD I ain't into details;Thank goodness many people are and from those I learn.

 

[DonC]

I own the Scmidt and Bender 10-50 scope that suffers from temp shift. I solved issues by buying an adjustable pointer made specifically for this model. They sell a wide variety of pointers. It is a UK store called Maestro.

I now just calibrate the correct range with existing temperature. I also own 3 Nightforce Field Target fixed 36X scopes. These are not affected by temperature. I assume the fact that they are fixed power is the reason.

 

[CampFussell]

https://hardairmagazine.com/ham-columns/compensating-for-riflescope-temperature-shift-in-field-target-competition/

 

[John "spysir" Blount]

leupold 45x 84 degrees add 2 click's up. Thero strip tapes are good. 



John

 

[travelbike]

Thanks for all the reply. Looks like more testing next time I'm back in the man cave. BTW, I have my Tac Vector 10-40 scope mounted on a 12 fpe springer HW97. Will also test for pellet speed at the same time I check for shifts at different temps. Will report back. Understanding the quirks of your scope and air gun is a lot harder than figuring out the wifey.

 

[wheelie]

Thanks for all the reply. Looks like more testing next time I'm back in the man cave. BTW, I have my Tac Vector 10-40 scope mounted on a 12 fpe springer HW97. Will also test for pellet speed at the same time I check for shifts at different temps. Will report back.  Understanding the quirks of your scope and air gun is a lot harder than figuring out the wifey.



Guess you don't know my wifey! LOL

 

[Guest]

My Sightron shifts as well. One method to keep it at a more or less consistent temp is to keep it covered, and if possible out of the sun. This of course doesn't keep stop the ambient temperature from messing with things but helps eliminate some variables.

I accomplish this by using a gun bag that accepts the entire rig inside of it and keeping it in ths shade when not in use during a match. On courses with more sun than shade I try to keep it under an umbrella as well. If you use a gun caddy a simple white towel will do. Though I've seen some flip over covers made from windshield deflectors.

Also, for me I make a new range tape every few months to accommodate average temps and changes in my eyesight.

Your best bet for mapping your scopes temp shift will be to use it on a pcp for testing, if you HF ave one. I say this because your HW is going to shoot faster or slower depending on temp as well and you don't want to confuse the two.

 

[jwrabbit123]

Hi , Well , I read all replies and I have to disagree with all of it , I have a very different opinion on this , First off lets address parallax this was not meant to be a ranging tool ever , your reticle was for a skilled marksman , you use your mils or moa to range to bracket targets ,

p/s We all know ther is range finders but say battery goes dead , or you cant use range finder to get the zombie that is coming after you as he will know your position when you hit that range finder , or it can break or go dead , this is why it is good to learn to range by reticle , also ,



Everyone mentions temperature and scope shift , well temperature changes your feet per second just like ammo temp and air temperature , these are all inputs to make your final firing point ,Temperature can change speeds dramatically ,

Exampls if you say had your DOPE SHEET at 50 degrees temp and it was say 90 degrees out and ammo was in hot sun and barrel temp is warm , and every other correction was spot on and you shot 2500 yards you would miss your target by over 7 feet . so temperature is a huge factor to anyone who shoots long distance or to someone who has to calculate a final firing position to make a 1 shot hit 



OK back to temperature , when temp goes up and down , things expand and contract as well , so harmonics , barrel droop can change alot more things become variable

There is alot more data which goes into ballistics it is all Math for calculating ,

As for a bad scope well maybe some just had a bad scope or poor quality optics they just are not accurate for dialing ,and better to zero and hold , I have optics I dial and optics I just zero and hold for ,

LOU

 

[Guest]

To each his own. Though every serious FT shooter for the last 40 will disagree.

 

[Scotchmo]

To each his own. Though every serious FT shooter for the last 40 will disagree.

You can use the parallax adjuster to estimate distance to target. And it can be fairly accurate, especially if you have a large objective and high magnification, and you only need to estimate fairly close distances (10-55 yards).

Outside of a very few FT specific scopes, manufacturers do not promote/advertise that ability. In general, range estimating is not the intended purpose for the parallax adjuster.