Temperature effect on accuracy

[Bluecup]

Hello,

I am having some problems with my S410 xtra fac .22 with a Hawke sidewinder on top. I have been shooting at 25 yards and getting some changes in accuracy from the afternoon to early evening. I think the temperature is effecting my zero, I am shooting pin wheels when it is warm and then once the temperature drops I am -1 to -2 on small bore rifle targets. Is it normal for this change from the temperature or am I missing something. I do not recall having this problem before. Any help or suggestion would be great.

Thank you,

Jim

 

[T_Farrar]

Welcome to airguns. This is the most frustrating thing in existence. I have the same issues. Drives me insane 

 

[Imold]

Cold weather will effect POI due to different air density, pellets will start hitting lower.

 

[T_Farrar]

Wondering if these new redwolfs that are digitally regulated auto-compensate for the differences in temperature to adjust velocity? 

 

[nervoustrig]

The only time I've experienced a noticeable POI shift at such short distance (25yds) with a PCP is when the hammer was lubricated with something that changed viscosity substantially.

For example, this is an experiment I did last winter on a rifle that I had zeroed in the summer. The difference in temperature was at least 40 degrees F.

http://i.imgur.com/0c12s75.jpg

Some discussion around the subject at the time https://www.gatewaytoairguns.org/GTA/index.php?topic=134046

 

[Imold]

Wondering if these new redwolfs that are digitally regulated auto-compensate for the differences in temperature to adjust velocity?

Hope someone chimes in that’s a good question.

 

[Coldair]

Try switching to a different scope and see if that solves your problem. It is a little known fact that some scopes can be affected by temperature.


CA

 

[Guest]

The issue is likely your barrel band interfering with the shroud. You can identify this by looking at the clearences between the shroud and band at different temps and fill pressures. One method to alleviate the issue is to remove the oring and remove material from the inside of the barrel band. If that doesn't help enough the next step requires a bit more work.

You will have to empty the air tube. Heat the end of the tube at the valve assembly and loosen the air cylinder. When retightening it stop as soon as it contacts the valve body. So barely hand tight. Refilling will lock it in place. This allows the steel air cylinder and aluminum valve body to move with temp and pressure shifts without binding. Good luck.

John

 

[elh0102]

When I was shooting benchrest with metallic cartridges, the temperature and other weather variables would definitely affect velocity, so different powder types, primers, and charge amounts were required. I don't do any serious BR shooting with air guns, but I expect one just has to adjust hold for POI, maybe a slight change in hammer spring tension. 

 

[18.13]

Put the data into Chairgun. I was shooting last winter at 15 degrees and this summer at 109 degrees the difference was .4 mills at 100yds that's 1.4 inchs

 

[John "spysir" Blount]

As long as nothing is loose I would not think it is the rifle itself as this model is not know to suffer this problem Spend some time thinking about your scope & mounts. 

Get it to repeat & see whats whats. Temp strip on airtube & shroud & scope , you'll run it down.





John

 

[nomojo65]

I’m confused I guess?, is it accuracy or point of impact changes w/temp?, because POI will definitely change with temp., humidity a crosswind can even change vertical depending on direction and R or L twist of barrel rifling! POI can even change from tin or lot of same weight/ brand of pellet, the accuracy side of this equation I’ll let someone else handle...

 

[SMH77]

Temperature will affect both muzzle velocity, and your BC (which will affect your velocity at distance).

When it it warmer-say 95F-your muzzle velocity will be higher (say 905 fps), and the pellet will slow down less at distance (say 795 fps at 50 yards). When the temp drops to something like 40F, your muzzle velocity will drop (less energy in the compressed air) (say down to 880 fps) and the pellet will slow down faster (say down to like 755 fps at 50 yards) due to the denser air slowing the pellet down more rapidly. These changes in your 50 yard velocity show up in your measured BC. The result (without adjusting anything) show up in your point of impact dropping due to both the slower muzzle velocity and the more rapid deceleration due to the more dense air (drop in BC).

Hope that helps better understand why your POI will shift with temp (and environmental) changes.

https://www.airgunnation.com/topic/bc-variation-of-25-caliber-jsb-heavy-mk-i-pellets-with-changes-in-conditions/



Sean

 

[Bluecup]

First off thank you all for helping me out with a bunch of things to check. I would like to clarify a little bit as to what happens as it gets colder, I am not just getting a drop in velocity although that would make sense, I am going from dead center every shot to going low high left and right. The next day when it is warm out without touching anything I am back to hole in hole dead center again. I am starting to think I should just move to some place that is always hot, that will solve everything.

Thanks again,

Jim

 

[Coldair]

IF ALL ELSE FAILS...

If it is consistantly doing what you said it is doing then I would attach a thermometer to the gun and tape a note for the the clicks for both turrets required to rezero your scope in accordance to the relative varying temperature at that given moment you shoot. That is if your scope is not the culprit of course. It is what I do when switching different ammo types using the same gun to compensate for different POI except for using a thermometer.

Or I would just give up and sell it as-is and disclose what you experienced to the buyer and maybe someone living in a hotter enviroment gets it and then try another gun brand or model or both which no one has ever complained about. It would sure as heck be cheaper than packing up and relocating to keep it.



CA

 

[Hookster]

Wondering if these new redwolfs that are digitally regulated auto-compensate for the differences in temperature to adjust velocity?

Hope someone chimes in that’s a good question.

My RW HP encounters the same issues as every other PCPs with temp changes. The gun is advanced but not that advanced. 

 

[functor]

First off thank you all for helping me out with a bunch of things to check. I would like to clarify a little bit as to what happens as it gets colder, I am not just getting a drop in velocity although that would make sense, I am going from dead center every shot to going low high left and right. The next day when it is warm out without touching anything I am back to hole in hole dead center again. I am starting to think I should just move to some place that is always hot, that will solve everything.

Thanks again,

Jim

It's what John in Ma wrote-- I have used 3 AA 410's so far and any wandering zero was almost always because of the barrel band. If you loosen the band, almost always you'll see the shroud actually move. I allow the shroud to achieve it's natural alignment and then snug the band without letting it pull the shroud 

It could also be the scope mounts depending on how you mounted the scope, but I'd suspect the barrel band would be the primary cause of such shifts. 

 

[SMH77]

A fully free-floated barrel is definitely the way to go. Thermal contraction can definitely preload a barrel and reduce accuracy.

Once your setup is sorted out, you will still have some predictable shifts due to environmental conditions as noted above.

Keep us posted on how things turn out...

Sean

 

[DBrickashaw]

A few weeks ago I had the same thing happen, but POI changed due to rising temperature. Someone suggested increasing hammer spring tension and that mostly fixed the issue, but ended up swapping scopes to test the theory. It was happening on my Hawke Airmax, swapped to my Aztec and no more change in POI. Might be a Hawke issue.