Shooting High Due to Weather and Elevation?

[Josh Smith]

Hello,

I sighted in my rifle (Savage Mk II .22 BTVS) in dead calm conditions. I zeroed it in at 50 yards, and with a few clicks' adjustment in elevation only, I was making very close to 1moa hits with junk ammo at 100yds.

This was shooting a couple degrees UP, laying prone.

Last night, it stormed hard. The town flooded out, and I was fighting flooding conditions here in the country.

Today, it is much, much less humid. When I sighted it in before, we were anywhere from 88% to 99% humidity, dead still.

Today, as I said, less humid (it's all in the creek!) and I have an eight to 10mph wind blowing.

I decided to shoot a few things from my alternate perch, which is about three feet higher than my usual shooting spot. It put me dead inline, or slightly above, my targets at 50 yards.

It looks like I'm hitting about 1/2" high.

Now, I know the POI raises when you shoot uphill, but by this much at 50yds?

I need less variables. I need to shoot from the same spot from which I sighted, but unfortunately I cannot post new targets since the humidity is now in the creek, which I must cross in order to get to even my 50 yard target holder.

So, in short, here are the new variables:

1. Sighted in at 50yds in dead still conditions. It is now 8-10mph from the east.

2. Changed from shooting slightly upwards to straight or slightly downwards, which is less comfortable for me.

3. Humidity is much less than previously.

Would the above factors combine to give me a higher POI with the same ammo? As I said, isolating the factors is kinda' out of the question right now.

Thank you,

Josh

 

[TOP PREDATOR]

Re: Shooting High Due to Weather and Elevation?

the uphill / downhill thing would be my 1st thing to consider, followed by temperature and the humidity (thickness) of the air, even at 50 yards with a rimfire

the widn would create more of a left to right anomoly

 

[Josh Smith]

Re: Shooting High Due to Weather and Elevation?

I agree about the wind thing... it drifted it about half an inch to an inch to the right.

Now I just have to figure out how I want to zero the 'scope - at an upward angle, downward angle, or straight on... seems like straight would make the most sense to still hit the target uphill or down.

Thanks!

Josh

 

[dareposte]

Re: Shooting High Due to Weather and Elevation?

I'd guess it's probably the wind, a cross wind is known to raise or lower the impact of the bullet depending on the direction and the twist direction of your rifle... its like the curve ball effect in baseball. A MarkII is RH twist barrel, and a wind from the east (assuming you're shooting North) would raise tend to raise the POI slightly. A full moa of change due to humidity or the described change of shooting angle seems unlikely in my opinion.

Lower humidity makes denser air, and would tend to LOWER the point of impact. Shooting at the same distance on the level would also tend to LOWER the point of impact as compared to shooting up-hill. Temperature effects would most likely be negligible as described at 50 yds.

*Edit

Also you said you're shooting across the creek, and creeks can have drafts coming up off them in warm weather, and all kind of unexplainable weirness can happen in my experience.

 

[Josh Smith]

Re: Shooting High Due to Weather and Elevation?

Thanks folks.

The wind was actually from the NE, but the house was shielding the northern part of the NE, though it was likely creating eddies in doing so.

I was shooting from north to south.

Good point on the NPA varying. I noticed that if I shot at tree branches, changing the barrel elevation to maybe +15 degrees, I was back on target for the most part.

Thanks again,

Josh