temp and velocity

[bruno t]

I did a test with magpro and my 270wsm in my select grade kimber, 72 grains magpro moly coated and 150 grain berger, at 70 degrees I got 3,216 fps. I then put 5 rounds in the freezer for 30 min. I have a range 20feet out the backdoor. The velocity dropped to 3,130 so almost 100 fps less! Just a test.. So it didn't have a chance to warm up outside.. I'm still dumbfounded, on how I'm getting 3,040 fps, with the 180 grain woodleigh bullets and magpro..

 

[Capt RB]

If your going to continue with magpro or any temp sensitive powder for that matter. Buy a temperature gun like used by auto mechanics. Then use that to map out what the temp of the ammo actually is and record it in your data book. There are formulas to keep a bullet in a preferred fps as it pertains to an accuracy node.
As far as the 180's and magpro. The extra resistance is a plus for this powder.

 

[bruno t]

From what I'vefound all powders have some kinda loss in velocity in ddecreased temps! And a increase in velocity with hi temps. But they say its not temp sensitive.. Even if the velocity is 25fps less in cold weather. On the other hand it could be the barometric pressure, or humidity is higher or lower when I check rounds..its never the same unless it is on a day that I've tested with weather the same. I like magpro because the fps are + or- 10 fps from round to round when testing..