7mm AM WC872 and temp sensitivity?
To save some time and barrel life sending rounds down range, does anybody have any data that they'd like to share on how temp affects this powder?
Here's why, and my observations.
Shooting 180g Bergers, 45°F 770' elevation MV 3350 fps. for load development and sight in at home. Everything is great. loading 108.0 grains WC872
Went to Colorado for a cow elk hunt in December. Since elevation was a wee bit different, I ran rounds to verify drops. Started at the 300 yd zero, adjusted that zero for the different elevation then ran it all the way out to 1334 yds. Very happy with the way it performed. 39°F ambient, 6600 ft elevation, less than 1 moa wind adjustment for all shots. Made a drop chart for every 100 yds.
Nothing the first day of the hunt, 2nd day we stayed inside because it was snowing and blowing. Ended up with 24" of snow in less than 24 hrs.
The next morning it was -17°F at the lodge. We went down the hill, and to make a long story short ran into the cows at 5,000ft elevation. Temp at that time was -8°F. Dead calm, at the most 2-3 mph winds. Shot twice at 500 yds, aiming for a heart shot. Nothing. At the 2nd shot, the group came towards us and went into a canyon. When they popped up they were very close to 600 yds out. Dialed up, sent one. Nothing. WTF???
Again, they came towards us, dropping into a canyon for a while. We moved up, and finally saw the group again, this time at 700 yds. My spotter told me what to dial according to the drop chart and then said "wait a minute. Dial in 2 more moa". I did, held for a high shoulder shot and when the trigger broke the cow folded where she stood. The bullet went exactly where the crosshair said it should go. In retrospect, the only thing that I think was happening was the bullet was going under their belly, impacting on the other side of the herd. They heard the impact of the bullet hitting the ground on the opposite side of the herd, not the muzzle noise, and came towards us instead of going away.
Running the numbers in exbal here at the range yesterday in -10°F to +10°F it was a bear. 24+" of snow on the ground, flat terrain. Couldn't get a spotter and it was VERY hard to spot for myself. Could only shoot at 600 yds and 1,000 yds. Couldn't hit a 36" gong at 1,000 yds. Hit the 10" gong at 600 yds 2x out of 4 shots, could see that one of the missed shots was barely to the left (misread the wind). No bullet impact shown in the snow for the 4th shot. I was leaving the barrel cool for 20 minutes between shots.
Thoughts and advice??