Hi,

I've read of people tuning their powder charges for weather conditions.  Is there that much difference with smokeless powder in a .32-40 from day to day? 

I've definitely found that black powder loads that look good in summer will often tip significantly in the cold of winter.

I've only recently been using smokeless in my .32-40 and have what appears to be an excellent load, using 14.3 gr of SR-4759 and a 202gr Hoch bullet.  Is this load likely to perform much differently on a hot summer day vs. a cold one?   

Thanks,

Chris.

Thanks very much John.  I imagine that you are adding a bit more powder for cooler weather then? 

Chris.

Increase my powder load by a tenth grain in the winter.

Any other weather changes can be met by adjusting the breech seater depth.

JLouis,

I do percieve a mistake when you say that a higher temp has less moisture.  Relative humidity, maybe - but in absolute terms most certainly not.  The higher the temp, the more humidity it is capable of holding - and with a same moisute content, the lower the relative humidity will be for a same moisture content. So hot air with 20% humidity will actually carry more moisture than cold aier with the same RH.
However, colder air will be denser and offer more resistance

I want to know how you guys tune for wind 


I just searched my iPhone app store for IShooter and all I got was four video games. 

QuestionableMaynard8130 wrote on Mar 22^nd, 2015 at 9:06am:

My bad, sorry bout that

I found it in search using the following

Shooter (ballistics calculator) sean kennedy

It does automatic calculations for all the weather variables as well as altitude

Simply turn on/off the ones that are meaningful in your situation

What I'm suggesting is that the environmental factors cause changes to the velocity, BC and ultimately the stability of the bullet.

If you can monitor these effects then you have one more tool to affect an informed adjustment in your load.

I also suspect that once they have an accurate load they are comfortable with; a lot of shooters simply make small adjustments to their "hold" or tweak their sight settings a bit to component for bullet impact shifts due to velocity changes due to temp shifts rather than tinker with their powder 
measures or bullet seaters.

I suppose that if I were to go to the matches at Raton I might try to calculate a different powder charge based on the anticipated ambient temp differences from what I am used to here in the upper midwest.    And perhaps the desert conditions where one can get a pretty large temperature shift range from early morning to the heat of the day might require that.  
But here in the Upper Midwest (Etna 
Green specifically) it seems like we normally get a fairly modest diurnal temp range cycle---probably about 10 degrees or so.   Unless of course we are getting a significant "front" moving through; and those usually have enough wind that we have other things to worry about.