Results 1 to 14 of 14

Thread: Temp and point of impact

  1. #1
    Inactive Member

    User Info Menu

    Default Temp and point of impact

    Howzit
    One thing that I noticed at the nationals is that a lot of shooters complained about the point of impact of the guns shifting with the cold temperature in the mornings. So now my question is that if low temperatures has an impact will high temps have the same effect. If that is the case, what about using a temp gage and having different settings for different temps?

    Just wondering?
    Sign Up To Air Rifle SA Forums

  2. #2
    Protea FT Team '08

    User Info Menu

    Default

    At the last worlds there were poeople doing just that.Check the temp on the temp strip adjust a few clicks for the temp.

    Any material has an expansion coeficient.Change the temp enough and its size changes.
    Sign Up To Air Rifle SA Forums

  3. #3
    Inactive Member

    User Info Menu

    Default

    Fore sure it has an inpact with my .30-06 I have a 2 click change in POI if the temp drops with 10-12 gedrees. With a airrifle it is the same but I'm not sure by how mutch the POI changes. That you must ask the pro's.
    Sign Up To Air Rifle SA Forums

  4. #4
    Inactive Member

    User Info Menu

    Default

    Allan is right about the expansion thing. Just one more thing to remember, to make matters worse, lots of stress is applied when the rifling is formed (either by button cutting or hammer forge) and sometime the is barrel slightly out of line (the happens more often then most people think), they are straightened again and when the temperature changes, the stressed points tend to go back to it original shape. That is why target centerfires have heavy barrel is that they heat up slower and it is well known within the rifle shooter that they need to keep a few minutes between shots of the hunting rifle when sighting in the scopes.





    Also, if you use pellet lube, the viscosity can change.
    Sign Up To Air Rifle SA Forums

  5. #5
    Inactive Member

    User Info Menu

    Default

    My Steyr was shooting an inch low out at 50m during those cold morning on the weekend.

    Put it in the sun for a while and problem solved.
    Sign Up To Air Rifle SA Forums

  6. #6
    MCJ's Avatar MCJ
    Guest

    Default

    Spyker you mention that you put your rifle in the sun for a while?

    Are we thus assuming that it is the RIFLE and all its components that is cold and causing the drop in POI....OR is it the fact that the increase in density of the air, when the temperature drops, be the factor....

    I have spoken to Springbok Benchrest shooter Chris van Niekerk on this subject, and they do take this into concidereation with the bigger calibres, but I can not get a definite answer for air rifles :dunno

    This I know, when the temperature drops, your POI will drop lower....

    Maybe our technical director can help here with some concrete information...Urabus?
    Sign Up To Air Rifle SA Forums

  7. #7
    Inactive Member

    User Info Menu

    Default

    Remember, my barrel is not free floating and the chassis of the rifle is all alloy. When cold, the chassis contracts thus causing the shift in POI. I don't think that air density has such a big effect, unless you zero at the coast and then come up here to shoot.
    I'm not sure, maybe Urabus can answer this one.
    Sign Up To Air Rifle SA Forums

  8. #8
    Marksman
    The Guru

    User Info Menu

    Default

    I also read in quite a few posts that the Leupolds are extremely temperature sensitive and many overseas shooters actually have 2 sets of calibrations on their Leupolds for different conditions.

    Sign Up To Air Rifle SA Forums

  9. #9
    Inactive Member

    User Info Menu

    Default

    Almost everybody had shift problems, not only the guys with Leupolds.
    Sign Up To Air Rifle SA Forums

  10. #10
    Sharp Shooter
    The Professor

    User Info Menu

    Default

    Dieter,

    On your Steyr do you have a screw holding the barrel on the forward chassis extension as on the LG100's.

    From what I have heard over here people have found that easing this off so it is not gripping the barrel goes a long way towards alleviating POI shift across temp variation.

    Guido - have you any knowledge on that?

    Regarding air temp/density effect I have experienced a small variation summer to winter over here but only on the order of 0.5MOA drop.

    In respect of Leupold sensitivity - I have heard a lot about this but not experienced it. What I have found problematic is calibrating range markings in extremes of light conditions, when you go to other conditions then the marks are off.

    By picking a day with diffuse light i.e bright but overcast with cloud, to calibrate my range finding, then my range marking seem to remain stable across a broad selection of conditions.

    Dale
    <span class='smallblacktext'>[ Edited Wed May 10 2006, 09:32AM ]</span>
    Sign Up To Air Rifle SA Forums

  11. #11
    Inactive Member

    User Info Menu

    Default

    Yes there is a screw. I haven't tried that yet. It should work though, because the barrel is pretty thick.
    Sign Up To Air Rifle SA Forums

  12. #12
    Marksman
    The Guru

    User Info Menu

    Default

    The general consensus with the Steyr, especially with the new LG110 is to leave that screw well alone.

    Under that screw is a PTFE spacer which butts up against the barrel and which Steyr claim has sorted out the POI shifts experienced in the past.
    In older Steyrs the grub screw butted up directly [metal to metal] against the barrel.

    Spyker you can try and free float the barrel at your peril...but remember that unless you machine out that collar the barrel will not really be free floating.

    The Steyr barrel collars and breech mounting [front and rear] are an oval shape which makes 2 contact points on the barrel to allow it to be fixed in a very secure way....unlike other rifles.

    This also allows barrels to be interchanged very very easily and can accommodate 16mmOD barrels of varying tolerances....hence the perfect rifle!! hehe


    One more point to remember is that the POI shifts experienced by many overseas shooters happen in extreme weather where they shoot in sub-zero conditions quite often...
    Sign Up To Air Rifle SA Forums

  13. #13
    Inactive Member

    User Info Menu

    Default

    don't worry, I'm not about to float the barrel. It's only early in the morning that the problem shows itself and we normally shoot in the afternoon.
    Sign Up To Air Rifle SA Forums

  14. #14
    Inactive Member

    User Info Menu

    Default

    there are too many factors to consider........
    but as suggested above, many overseas shooters have different settings, but then they shooting in a wide temp range (sub zero to 30 dec C?). imho, the best thing to do is to set the rig up in the same condition as the shoot.

    personally, over the weekend.........i tried to check my zero as close to the start of the shoot as possible, allow the EV to soak up as much sun/heat as possible. by then.......i did not notice any change in POI.

    Sign Up To Air Rifle SA Forums


Similar Threads

  1. Changing point of impact
    By promnig in forum Airgun Discussions
    Replies: 11
    Last Post: 03-12-15, 08:39
  2. Temp effect on pellets ?
    By Yeti in forum Airgun Discussions
    Replies: 14
    Last Post: 02-11-10, 13:34
  3. Sideways Point of impact shift.
    By Sniperdad in forum Airgun Discussions
    Replies: 53
    Last Post: 16-04-10, 09:00
  4. Point of impact
    By CZ in forum Airgun Discussions
    Replies: 15
    Last Post: 09-05-06, 13:39

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  
Friends of Air Rifle SA