Temperature and scopes

[Grifff]

Been down the airgun range today and it was bloody freezing! I found that I had to dial 1 1/4 moa to correct my poi which is more down to the gun I expect but when parralaxing for range finding it was also noticeably out.

This is not uncommon with field target but my old gun and scope combo didn't suffer with temp.

Anyway getting to the point on long range shooting do you find temp dramatically effecting scope, and if so how?

Grifff

[Sim G]

It’s not your scope, but the air density. Colder air is more dense and so the pellet or bullet has greater resistance to overcome. This affects your trajectory.

[snayperskaya]

It’s not your scope, but the air density. Colder air is more dense and so the pellet or bullet has greater resistance to overcome. This affects your trajectory.

humidity also plays a role in this density, as cold air is generally drier than warm air in a given location and contrary to what would seem logical, humid air is less dense than dry.

[Grifff]

I can understand what you're saying does this make a big difference and are there rules of thumb to work by? I had to add 10 clicks on the elevation today 1/8 per click. My barrel isn't floated yet though and attached to the air cylinder which is known to cause temp issues.
Temperature must effect the scope in someway as the parallax was certainly a few yards out which although easily compensated for in FT just got me wondering what else it might affect at longer range.

[Sim G]

No, unless you’re running a really naff scope, in really naff mounts, I can’t imagine it’s the scope. Atmospherics on the flight path of your pellet. Likewise, atmospherics on a PCP cylinder again, can’t be discounted. Your scope should be nitrogen filled so that the effects of atmospherics and the changes in temperature and pressure are negated.

[Fedaykin]

Also handily explained in Ice Station Zebra:

https://www.youtube.com/watch?v=jMj78kKv5RA

[Sim G]

Also handily explained in Ice Station Zebra:

https://www.youtube.com/watch?v=jMj78kKv5RA

Best answer ever!

[Grifff]

Excellent. But we are only talking 55yds .25s flight time. Next time I'll try it over the chronograph out of interest.
Scope wise falcon t50 so middle range £400 scope.
But why would it effect the parallaxing?

I'm not concerned just interested I know lots of shooters who also have found this you can even get multi pin pointers for range finding due to temp, but like I said my old setup didn't seem to suffer from it.

Oh well you know what they said about curiosity:-)