Range Report Question on changing dope

[bassmaster07]

New to longish range shooting. Yesterday was second time out to 600. First time was in October. Just figuring out how to set up apps and all that. But had a question.


shooting in TX. 6.5 tikka CTR 24” shooting American gunner 140.
In October my dope was the following:
500 yards 3.4 mil
600 was 4.4 mil
Mild day with little wind.

Yesterday
500 yards 3.7
600 yards 4.9 mil
Windy and cold.

500 yard delta was .3 mil
600 yard delta was .5 mil.


Wind was easy to account for but all day my old dope and old trued loads from October where low.

Is this kinda change based on weather alone normal? Same lot of ammo. Same exact set up as before.

Guessing not but I really do not know.

Also have never held 1 mil for wind before and that was really cool.

Pic of range attached from October (no targets set up at 400). Range has targets from 200 to 600 at every 100. Shooting prone from second level porch. So am able to walk out to 600 figuring out wind and drop as I go.

 

[ShtrRdy]

Colder temps will make the air denser. Also the air pressure might be different from the time before. These could affect bullet drop.

 

[bassmaster07]

True. Yesterday was humid and temp wine t from 42 to 59.

But would weather alone be enough to cause that much difference at 600?

 

[VP47PPC]

Read up on density altitude. Three main factors are pressure, temperature and altitude. I just shot a PRS match yesterday and Density Altitude was 1720 ft. At the same range this summer the density altitude would run around 4000 plus feet, but as I run my ballistic app I get a 1/4 MOA difference so ???

 

[_Windrider_]

Read up on density altitude. Three main factors are pressure, temperature and altitude. I just hot a PRS match yesterday and Density Altitude was 1720 ft. At the same range this summer the density altitude would run around 4000 plus feet, but as I run my ballistic app I get a 1/4 MOA difference so ???

You a p3 guy?

 

[ShtrRdy]

Something else that can change is when the powder is cooler it generates less pressure and therefore less velocity.

Trying running a couple ballistic solutions on JBM Ballistics. It's an online program.

 

[VP47PPC]

You a p3 guy?

Yes, Moffett 83/86

 

[VP47PPC]

Last week went to the 500 yd range to verify my zero and was 3/4 moa high. Rather than check zero at 100 I just reset zero off 500 yd shots. At match yesterday was dead on. Dope was good needed new zero. This happened back in OCT went to verify zero and was 1moa low. Why I don't know, but reseting worked for match the next day.

 

[_Windrider_]

Yes, Moffett 83/86

Ah old school. I was VP4