GTA
Support Equipment For PCP/HPA/CO2 and springers ,rams => Optics, Range estimation & related subjects => Topic started by: prosportfan on August 01, 2017, 03:14:33 PM
-
I was just wondering, let's say if you calibrated/marked your scopes side wheel or front AO in 60° weather from 10-55yds and then on a 90° day you have a match or just decided to target shoot and your target is 20yds away. You adjust your AO/sidewheel to the 20yd mark that's labeled. Does it seem like it's off? Maybe a little blurry or the "head bob" technique shows movement within the scope? I am just wondering how much does a temperature change effect the parallax or the parallax's adjustment.
-
I noticed you haven't gotten a response on either forum on which I saw your question. It may help if you give some context. If you are having a specific problem, please describe it. What are your expectations...hitting the tiny 10 ring at a benchrest competition or performing a lobotomy on a ground squirrel at 50 yards?
To give my perspective, I shoot year round in temperatures ranging from 20F to 100F. My most accurate rifles are regulated PCPs in .177 and .22 caliber. In calm conditions, they will group very closely to the nominal zero regardless of the temperature outside, which of course spans a number of variables besides scope parallax. My expectations are to be able to hit small targets like Mardi Gras beads and hickory nuts and things of that nature, for example:
http://www.youtube.com/watch?v=hkvblVB1zzI&feature=player_embedded#ws (http://www.youtube.com/watch?v=hkvblVB1zzI&feature=player_embedded#ws)
-
You're right. I was in a rush because of rain. I don't have a problem per se but I was just wondering, let's say if you calibrated/marked your scopes side wheel or front AO in 60° weather from 10-55yds and then on a 90° day you have a match or just decided to target shoot and your target is 20yds away. You adjust your AO/sidewheel to the 20yd mark that's labeled. Does it seem like it's off? Maybe a little blurry or the "head bob" technique shows movement within the scope? I am just wondering how much does a temperature change effect the parallax or the parallax's adjustment.
-
I wouldn't think that parallax would be affected by temperature but pellet ballistics would. As to what extent is hard to say. Warmer air is thinner but can hold more moisture. Colder air is thicker and holds less moisture.
If you're using a pcp or co2 you could see a reservoir pressure difference and this can produce different pellet velocities when comparing hotter versus colder temperatures. Again to what extent would need to be tested.
When you initially stated temperature my brain thought about mirage. I have read that magnifications above 16 power will be affected by mirage.
I hope that helps.
Thanks,
Taso
-
Thanks taso
-
I haven't noticed much parallax change. I have noticed POI change with temperature. When I bring the gun out of the AC in the house it will be off 3 or 4 clicks high and right at 30 yds. as the gun warms up it returns to where it belongs. If you leave it out in the sun it goes 3 or 4 the other way. When at a match I keep the scope covered with a towel, this helps a lot.
My HW100 tends to move a little more then my Steyr.
Tom
-
Tom,
Is it possible the barrel shifts position slightly as it warms up versus the scope?
Thanks,
Taso
-
I haven't noticed much parallax change. I have noticed POI change with temperature. When I bring the gun out of the AC in the house it will be off 3 or 4 clicks high and right at 30 yds. as the gun warms up it returns to where it belongs. If you leave it out in the sun it goes 3 or 4 the other way. When at a match I keep the scope covered with a towel, this helps a lot.
My HW100 tends to move a little more then my Steyr.
Tom
I will have to see if my poi changes Tom. And I was wondering why people at the march I met you at were doing that. Hey I got my 54 back from John in PA and she is spectacular
-
I haven't noticed much parallax change. I have noticed POI change with temperature. When I bring the gun out of the AC in the house it will be off 3 or 4 clicks high and right at 30 yds. as the gun warms up it returns to where it belongs. If you leave it out in the sun it goes 3 or 4 the other way. When at a match I keep the scope covered with a towel, this helps a lot.
My HW100 tends to move a little more then my Steyr.
Tom
I have noticed the same thing with POI shift. I was thinking that the thermal expansion of the steel barrel is different from the thermal expansion of the aluminium rings and possibly the material that the scope is made of as well. This would cause the shift in POI. If everything was made from the same material, then I would think that all of them would move together, and we as shooters wouldn't notice. It would also explain why some guns tend to be more temperature sensitive than others.
-
I haven't noticed much parallax change. I have noticed POI change with temperature. When I bring the gun out of the AC in the house it will be off 3 or 4 clicks high and right at 30 yds. as the gun warms up it returns to where it belongs. If you leave it out in the sun it goes 3 or 4 the other way. When at a match I keep the scope covered with a towel, this helps a lot.
My HW100 tends to move a little more then my Steyr.
Tom
I have noticed same thing.
If bring gun out of AC it will shoot high, and POI starts to lower as gun warms up. Below is a thread about an HW85.
https://www.gatewaytoairguns.org/GTA/index.php?topic=126208.0 (https://www.gatewaytoairguns.org/GTA/index.php?topic=126208.0)
-
There is something expanding and contracting, but I can't figure it out. I tried floating the barrel on the steyr didn't help much.
Tom