Temperature effect on elevation adjustment

[EOS]

Im seeing a big effect on my elevation adjustment this year. At 700 yds I usually dial 15 MOA at 60*F, Its around 75-80*F right now and Im having to dial down to 12.5 MOA. This seem like a normal adjustment for 15-20* temp change?

7mm WSM 180 Berger. 6500' elevation. No wind change.

 

[seanmyhre]

Re: Temperature effect on elevation adjustment

I'm fairly new at the long distance shooting game, but my first question would be what powder are you using and is it temp sensitive?

 

[yoterunner]

Re: Temperature effect on elevation adjustment

I am also interested in changes due to temp. Where do you get data about sensitivity of the various powders?

 

[427Cobra]

Re: Temperature effect on elevation adjustment

Search Density Altitude and/or DA cards, your gonna need a Kestral 4000 or another device to give you DA

 

[EOS]

Re: Temperature effect on elevation adjustment

Shooting h1000.

Im looking for a rule of thumb kinda thing. Colder air more dense, slows bullet down?

 

[LARMIKE]

Re: Temperature effect on elevation adjustment

20 Degrees up or down = 1 MOA. on average.

 

[seanmyhre]

Re: Temperature effect on elevation adjustment

I've never seen a database or comprehensive list of powders and their temp sensitivities. Most of the one's I've found have been pistol powders, but I know some rifle powders can do the same thing. Winchester powders are netoriously reverse temp sensitive. WST is one that I have tested a little for this and found it to fluxuate quite a bit from 80 degrees to 20 degrees. It seems the nitroglycerine (double-based) powders seem to be more affected by temp changes than the nitrocellulose (single-based) powders, but I've seen a little swing in velocity from some single based powders too. Not having very much experience with this anomoly with the various rifle powders, I was hoping for some input by others may render info relevant to your issue.

 

[BobinNC]

Re: Temperature effect on elevation adjustment

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: EOS</div><div class="ubbcode-body">Im seeing a big effect on my elevation adjustment this year. At 700 yds I usually dial 15 MOA at 60*F, Its around 75-80*F right now and Im having to dial down to 12.5 MOA. This seem like a normal adjustment for 15-20* temp change?

7mm WSM 180 Berger. 6500' elevation. No wind change. </div></div>

EOS,

Not sure what you are doing, but when I run JBM using a 180 Gr Berger @ 3000 FPS Using Litz G7 calc's, and 6500' ASL, I get drops of 12.6 MOA @ 700 yds.

Not sure how you got 15.0 MOA. Your bullet would have to be traveling at 2775 FPS or less to show 15.0 MOA @ 700 YDS.

What velocity are you using?

Bob

 

[Lindy]

Re: Temperature effect on elevation adjustment

See:

http://shootingsoftware.com/ftp/Pressure%20Factors.pdf

 

[ranger1183]

Re: Temperature effect on elevation adjustment

Lindy, you're back!

 

[trigger time]

Re: Temperature effect on elevation adjustment

Welcome back Lindy

 

[seanmyhre]

Re: Temperature effect on elevation adjustment

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: RJ Hunter</div><div class="ubbcode-body">It is not just the powder. It is the powder - primer relationship. They both play a part in this. </div></div> I haven't found this to be the case at all with the pistol reloads I have tested. Can you elaborate, please?