MRP and temp sensitivity....

[Mr.Knowit all]

Hello,
I have had great luck with MRP as of late. Had my 300 re-barreled 2 mos. ago, found a great load and have been shooting almost every other day since. It has been hot in Nevada so the other day I wanted to beat the wind and heat/mirage so I headed out about 6:30 am. It was 58 degrees that morning, at least 30 degrees cooler than when I am able to get to the range. I had almost 60 fps less that morning than I usually have. 60!!!! I could not figure why I was off so bad on my long shot (1784 yds) So I hooked up my Magnetospeed and found out my Velocity was way off. My SD was still low but I am at a loss for the velocity difference.
I know there has been many articles on powder and temp. sensitivity but has anyone had an issue like this with MRP in particular?
Thank you,
Eternal

 

[boltfluter]

Yes, if I am thinking clearly. Most ball powders are very temperature sensitive to the tune of about 2 fps per 1 deg of temp change. If you know the exact ratio it is not to hard to compensate. I personally do not run ball powders for this exact reason on a hunting rifle. Way to aggravating when hunting. Not a big deal with target shooting.

Paul

 

[wboggs]

Yes, if I am thinking clearly. Most ball powders are very temperature sensitive to the tune of about 2 fps per 1 deg of temp change. If you know the exact ratio it is not to hard to compensate. I personally do not run ball powders for this exact reason on a hunting rifle. Way to aggravating when hunting. Not a big deal with target shooting.

Paul

I don't think Norma MRP is a ball powder.
Bill

 

[Rstrick0352]

I don't think Norma MRP is a ball powder.
Bill

It’s a stick, double based powder. I use it for .243 shooting 105amax and it responds similarly to H4831.

 

[boltfluter]

You guys are right. I was thinking of WMR powder. My bad!

Paul