Temperature effects on POI (scope issue)

[thonayan99]

Greeting all,

In conclusion: if you have any sever shift in POI simply try to change your scope to another one. Definitely weather temperature will have affect on your POI but not that much to worry about for 50 yards and below during hunting or shooting. 

the Hawke scope drive me crazy during hunting and I kept re-zeroing my scope across the whole day. when analyzing the data I found that the scope have a problem probably the scope internal spring is affected by the rapid change in temperature. Doing some back calculation on the maximum extreme shift level in POI, the fx impact must increase the slug velocity to 1520 fps to reach this shift level while there was no change made during the hunting to the airgun! so it is almost impossible to happen that velocity have dramatic increase during the hunting. Then decided to change the scope and now I am satisficed with the result, the POI was shift but in acceptable level to me. 

Attached chart show all the details and the result after changing the scope. 

FX impact MK II 700MM HP Slug 23 gr @ 925 fps :

regulator pressure @ 130

wheel @ 2

valve 1 1/2 turns

 

[allenbowles]

interesting data,have you had hawke check your scope?

 

[steve123]

Something might be wrong with the gun too. Or maybe a combination of the scopes and the gun??? Because with a 30Y zero you should only have .1 mil drop to 37Y.

I've shot from mid 30 degrees F to 100+ degrees F without any shifting, or I should say not enough shifting during a FT match to miss a target. Scopes included S&B 5-25, leupold 40x fixed, B&L 8-32 ,and Athlon Argos BTR 6-24. Average temps were 50's to 90's though.

I distinctly remember winning a match during a snowstorm and winning another one when it was so hot I almost quit and left!

 

[Odoyle]

Not surprised one bit with HAWKE...

https://www.airgunnation.com/topic/problems-with-yet-another-hawke-scope/

 

[thonayan99]

Not yet

 

[thonayan99]

Therotically there must be a shift more than 0.1 mil. According to sterlock app and chairgun the shift is possibel to be from 0.3 to 0.5 mils due to wather temp change. But maybe you are right about the gun issue since i have 0.75 mil shift which is littel bit higher by 0.25 from the therotical calc max shift. 



Thnx for your feed back.

 

[steve123]

There is no way in the world that there would be a .6 mil shift let alone a 1 mil shift from 26 to 37C, I don't care what chairgun states. I've been shooting FT for 23 years and if there is a shift that large, well, ouch!

You definitely have a problem, what I don't know for sure.

I'll tell you this - Impacts do have POI shifts. Rubber orings holding a flimsy liner centered in a tube and then fastened by one rear grub screw is, well, silly IMO.

Then compare that to my USFT which has a barrel clamped into 1.5"?? of machined aluminum using two huge bolts. 

 

[thonayan99]

Thanks for the info and sharing your experaince..hope to hear from others fx impact mk ii owners if they do have similar poi shift by like 0.5 mil or not during weather temp changes. 

 

[Odoyle]

Send that HAWKE in for a warranty exchange and sell it.

 

[Bluecup]

I had the same problem with my hawke sidewinder 30. send it back and have it checked.

 

[Odoyle]

Sure hope the new much more expensive HAWKE scopes have WAY BETTER QC than the current ones...