How much does ambient temperature affect 17hmr?

[Geezedtee]

Yesterday and today I was sitting over growing Maize shooting squirrels that were trying to eat it.
Yesterday some of the shots were low but I put it down to them being between 85 -100 yards and a flat feature less field where it was difficult to accurately laser the range. Today first 4 shots -between 65 and 85 yards also missed low.
I picked out a white stone at 45yds and the shot was again low by an inch. Aimed at the top and hit smack in the middle.
I went to our little range and put a target up at 50yds. Checked all the screws were still torqued up correctly. Shot off a bench and got a 3 shot ragged hole at 1" low! I then repeated that and re-zeroed the scope.
It's a Tikka 1x in a synthetic stock. It hasn't been knocked or dropped. Scope set the same. All screws were the same torque as when I set up the scope and rifle last November. Same batch of Remington Accutip ammo. The rifle is grouping well (1/2 moa at 100yds - apart from the odd flier). The scope tracked accurately as I adjusted the MPI.
All my previous varmint shooting has been during the winter and spring and at night. The air temperature has varied between -5 and +10 degrees Centigrade. Yesterday and today the temperature was 28-30 and my rifle was exposed to the sun.
So my question is could the temperature change make that much difference to a 17hmr at 50yds??

 

[Bill K]

In my CZ 455, heavy varmint barrel I have not seen any change like that during shooting in heat of summer and cold of winter. It is also housed in a laminate Boyd's stock. I also shade my ammo from the sun.

But maybe it is just your rifle, if it has a standard or pencil barrel and the synthetic stock shifts the barrel with the change in temp.
Or possible your ammo sitting in the sun heats more, causing pressure change.

 

[J.D.Erwin]

Yesterday and today I was sitting over growing Maize shooting squirrels that were trying to eat it.
Yesterday some of the shots were low but I put it down to them being between 85 -100 yards and a flat feature less field where it was difficult to accurately laser the range. Today first 4 shots -between 65 and 85 yards also missed low.
I picked out a white stone at 45yds and the shot was again low by an inch. Aimed at the top and hit smack in the middle.
I went to our little range and put a target up at 50yds. Checked all the screws were still torqued up correctly. Shot off a bench and got a 3 shot ragged hole at 1" low! I then repeated that and re-zeroed the scope.
It's a Tikka 1x in a synthetic stock. It hasn't been knocked or dropped. Scope set the same. All screws were the same torque as when I set up the scope and rifle last November. Same batch of Remington Accutip ammo. The rifle is grouping well (1/2 moa at 100yds - apart from the odd flier). The scope tracked accurately as I adjusted the MPI.
All my previous varmint shooting has been during the winter and spring and at night. The air temperature has varied between -5 and +10 degrees Centigrade. Yesterday and today the temperature was 28-30 and my rifle was exposed to the sun.
So my question is could the temperature change make that much difference to a 17hmr at 50yds??

I have a few 17 HMR and I find in all of them the ammo being rimfire is what you get flier,Ive seem POI change from lot to lot and Mfr. to Mfr. I do keep my ammo out of direct sunlight in the summer but in the winter a little sun is a plus. I find a small scope adjustment is the quickest way to correct POI in the 17 HMR and 22 LR hope this helps.

 

[6ShotsOr5?]

Higher ambient temp could lead to a higher chamber pressure and higher MV. Higher air temp usually would lower the air density, and the bullet drag. Not obvious how either one of those would lead to shooting lower. Any possibility you are having a senior moment about some work on your stock or scope?

 

[Geezedtee]

Higher ambient temp could lead to a higher chamber pressure and higher MV. Higher air temp usually would lower the air density, and the bullet drag. Not obvious how either one of those would lead to shooting lower. Any possibility you are having a senior moment about some work on your stock or scope?

Hi. I have selective senior moments when the wife wants something onerous doing
But I'm anal when it comes to my rifles and shooting. I record all the screw torques and index mark them. Make note of my scope settings and mark the turrets at Zero with white Tippex. It is a slim sporter weight barrel and basic Tikka tupperware stock, but it is free floated. Both my ammo and me were in the shade of a hide/blind, but the front half of the rifle was exposed to the sun for about 4 hours. I understand the factors that may open a group up, but in this case the group size was consistent and POI just skimming under the squirrels (the 17 does let you see the impact).
It's not a big deal in the grand scheme of things, I just wondered if anyone else had experienced it and whether it was the heat.

 

[drover]

I would suspect that it was a different lot of ammo. I keep an eye out for subsequent changes, it may be that your scope internals moved and if they did it once then it is likely to occur again.

It doesn't inspire confidence does it?

drover

 

[Geezedtee]

I would suspect that it was a different lot of ammo. I keep an eye out for subsequent changes, it may be that your scope internals moved and if they did it once then it is likely to occur again.

It doesn't inspire confidence does it?

drover

Hmm. Same lot number of ammunition and a digital Zulus scope. I always check the right ballistic table is selected and the X Y numbers are as recorded. I will have to resort to more range shooting just to check it's OK.

 

[jxb]

I'm sure it does but I usually used my 17hmr as a walking gun so never noticed.