Difference in temp

[Jaimeb832]

Hello, so I zeroed my rifle in AZ when it was hot (105 degrees) today I went to recheck my zero and it was 65 degrees . My bullet at 100 yards dropped 2 inches. Is this normal ? I’ve always hunting and shot my rifle in California on the coast, the temps were never much different.

I’m shooting a 300 wing mag 185 grn Berger rounds.

 

[stello1001]

What powder are you using? Or is it factory ammo?

The Temps definitely change the air density and can play a bit with your dope. I just don't know how much it would affect it at only 100y.

 

[Jaimeb832]

Factory ammo, but. I also tried some handmade ones and same. Grouping was still good just low 2 inches

 

[TheJeanyus]

2" shift at 100 yards seems like a lot for a 40 degree temperature change. Was there significantly more mirage when it was hotter as well?

 

[Jaimeb832]

Maybe, I had my rifle on shooting bags sandbags days. Nothing moved

 

[Taylorbok]

I'd say you had a zero shift from something else, that's to much for enviro's

 

[Jaimeb832]

I'd say you had a zero shift from something else, that's to much for enviro's

Haven’t bumped it or anything.

 

[NateVA]

I'd say you had a zero shift from something else, that's to much for enviro's

This.

Haven’t bumped it or anything.

Your 100 yard zero is your zero. It should basically never change. I'm pretty sure the environmentals would have to be staggeringly different to produce a "click" worth of POI change at 100 yards. For instance I tried it out with my hunting rifle's ballistics (assuming a 50 yard zero just to see if your temp difference would change my 100 yard drop), and it didn't change the 100 yard drop at all.

1. Something got bumped and shifted your zero, could be one of these.

• Scope itself lost zero. What scope do you have on it?
• Scope rings slipped. What rings do you use?
• Scope base is loose. Have you loctited your scope base screws if the scope base is not integral?
• Barreled action shifted in the stock. What stock is it and is it bedded? Same questions if it's a chassis.

2. Your POI is changing because of drastically different management of the rifle, prone vs bench sort of thing.

 

[Jaimeb832]

This.

Your 100 yard zero is your zero. It should basically never change. I'm pretty sure the environmentals would have to be staggeringly different to produce a "click" worth of POI change at 100 yards. For instance I tried it out with my hunting rifle's ballistics (assuming a 50 yard zero just to see if your temp difference would change my 100 yard drop), and it didn't change the 100 yard drop at all.

1. Something got bumped and shifted your zero, could be one of these.

• Scope itself lost zero. What scope do you have on it?
• Scope rings slipped. What rings do you use?
• Scope base is loose. Have you loctited your scope base screws if the scope base is not integral?
• Barreled action shifted in the stock. What stock is it and is it bedded? Same questions if it's a chassis.

2. Your POI is changing because of drastically different management of the rifle, prone vs bench sort of thing.

First of thank you very much. I’ve hunted for many years but never really took too much noticed to a lot of minor details.

I have bergara premier rifle. I have a grayboe ridgeback stock and a night force shv scope with nigh force rings and base. I did zero my rifle on a bench on today I shot at the prone. Temp plus different shooting positions will make my bullet drop 2 inches ? The grouping is on point as both shots in both groups are touching

 

[Jaimeb832]

I checked all the scores and bolts and everything is on tight and loctite. Checked the torq specs as well .

 

[308pirate]

I checked all the scores and bolts and everything is on tight and loctite. Checked the torq specs as well .

It's you not the gun

 

[NateVA]

First of thank you very much. I’ve hunted for many years but never really took too much noticed to a lot of minor details.

I have bergara premier rifle. I have a grayboe ridgeback stock and a night force shv scope with nigh force rings and base. I did zero my rifle on a bench on today I shot at the prone. Temp plus different shooting positions will make my bullet drop 2 inches ? The grouping is on point as both shots in both groups are touching

Given this information I'd say it's you managing the rifle way different in the prone versus the bench you zeroed on.

 

[Jaimeb832]

It's you not the gun

You’re probably right boot ass gunny

Given this information I'd say it's you managing the rifle way different in the prone versus the bench you zeroed on.

Thank you , I’ll try the bench again just to confirm and zero for prone seeing that I will never hunt using a bench.

 

[NateVA]

Thank you , I’ll try the bench again just to confirm and zero for prone seeing that I will never hunt using a bench.

This is semi-related but if you don't already have a tripod you can shoot off of, consider getting one. Having a good tripod has changed everything about my western spot and stalk hunting. A few weeks ago both my father and I used my tripod to shoot antelope at 360 yards from a fully standing position since we couldn't get lower (two different locations/days, coincidence that it was same distance for both). Last year I killed a coues deer at 380 across a canyon using my tripod from the sitting position. It's a complete game changer.

 

[Jaimeb832]

This is semi-related but if you don't already have a tripod you can shoot off of, consider getting one. Having a good tripod has changed everything about my western spot and stalk hunting. A few weeks ago both my father and I used my tripod to shoot antelope at 360 yards from a fully standing position since we couldn't get lower (two different locations/days, coincidence that it was same distance for both). Last year I killed a coues deer at 380 across a canyon using my tripod from the sitting position. It's a complete game changer.

What tripod did you get ? I have one I use for my spotting scope and binos.

 

[Terry Cross]

Probably only 0.001% chance of this but are you sure you dialed your parallax out for the 100yd distance?

If you have parallax present in your system, you could easily get a 2 inch shift in POI at 100yds.

You said it was all vertical?

Your head position would be fairly upright/erect from the bench versus typically head rolled considerably more forward in a prone position. This would be exaggerated with a scope mounted low versus high. Even with identical cheek weld on the comb, this would position your eye differently in the vertical axis enough to cause a large POI shift while still comfortably in the exit pupil.

 

[NateVA]

What tripod did you get ? I have one I use for my spotting scope and binos.

Mine's kind of overkill/heavy/expensive. I use a TFCT-34L w/ Anvil ball head with a PT-Scout pan head that I clip into the Anvil for glassing. I can unclip the PT-Scout with my binos on it and have my rifle locked into the Anvil in about 5 seconds. But you could theoretically put a tripod together starting at $600 that would be lighter and stable enough for hunting situations.

Also, what Terry said.

 

[Jaimeb832]

Probably only 0.001% chance of this but are you sure you dialed your parallax out for the 100yd distance?

If you have parallax present in your system, you could easily get a 2 inch shift in POI at 100yds.

You said it was all vertical?

Your head position would be fairly upright/erect from the bench versus typically head rolled considerably more forward in a prone position. This would be exaggerated with a scope mounted low versus high. Even with identical cheek weld on the comb, this would position your eye differently in the vertical axis enough to cause a large POI shift while still comfortably in the exit pupil.

I’m going after work to shoot on the bench , hopefully the club out here is done shooting . I feel as though I was aligning everything correctly and the only thing that shifted was that I shot two inches lower . Left and right didn’t move at all

 

[Terry Cross]

I’m going after work to shoot on the bench , hopefully the club out here is done shooting . I feel as though I was aligning everything correctly and the only thing that shifted was that I shot two inches lower . Left and right didn’t move at all

Excuse me if this is an elementary question but I don't know your user level or experience.
Do you know how to check for parallax while your rifle is on the bench?

Parallax may not be the issue at all but it is simple to check. Easy way to find the culprit or eliminate one more possibility.

 

[Jaimeb832]

Excuse me if this is an elementary question but I don't know your user level or experience.
Do you know how to check for parallax while your rifle is on the bench?

Parallax may not be the issue at all but it is simple to check. Easy way to find the culprit or eliminate one more possibility.

I’ll check it out, from my understanding it’s the adjustable knob on the side of my nightforce has 100 to infinity .

 

[smoothy8500]

from my understanding

OK, we've narrowed down the problem...

 

[smoothy8500]

If your diopter is not properly adjusted, the focus and parallax may not be aligned and while the target image (focus) is crisp, there may be some parallax error present.

 

[Terry Cross]

I’ll check it out, from my understanding it’s the adjustable knob on the side of my nightforce has 100 to infinity .

Your NF may not have actual yardage numbers on the side knob and the range is likely closer to 35yds+/- to infinity.

 

[carbonbased]

I once was talking to some old dudes at the range and one guy said he “focused” the image with the diopter.

I gently suggested, no, that’s what the side knob is for, and the diopter is for the reticle. To his credit, a light went off in his head.

He probably just grew up with non-adjustable parallax and noticed the diopter had some focusing ability?

 

[Jaimeb832]

Your NF may not have actual yardage numbers on the side knob and the range is likely closer to 35yds+/- to infinity.

I figured out the issues . Wasn’t anything crazy. Every time I would go shooting and had the rifle sighted in here in AZ . It was plus 105 degrees. So the barrel was always “hot” . Today when I went the barrel was finally cold so my shots were lower. Once I got the barrel to warm up it started shooting a higher. Not sure if that makes sense

 

[carbonbased]

I figured out the issues . Wasn’t anything crazy. Every time I would go shooting and had the rifle sighted in here in AZ . It was plus 105 degrees. So the barrel was always “hot” . Today when I went the barrel was finally cold so my shots were lower. Once I got the barrel to warm up it started shooting a higher. Not sure if that makes sense

How many shots did it take to warm and and shoot where it used to?

 

[Jaimeb832]

How many shots did it take to warm and and shoot where it used to?

7 shots

 

[carbonbased]

7 shots

Hmmmmm…I’m no expert here, but…

…that doesn’t seem like very many.

 

[carbonbased]

Are you shooting a sporter-type profile barrel?

This is an old post about a similar thing:

Large change in accuracy with barrel temp

I have noticed a change in accuracy based on shooting in the sun or shade so Today I shot two different loads both in the sun and in the shade while evaluating differences in brass. Loads are all identical except for two different lots of brass. All components from the same containers, same...

www.snipershide.com

 

[smoothy8500]

Wasn’t anything crazy

Hmmmm, never is......