Originally Posted by Sake-San
Thanks Rob, that sounds OK, I have read all the historic posts but, just wanted the check what might have developed.
Did some more work today. Cold temps are rare around here... even today when rest of the country was scraping windscreens i didn't even have frost on mine. It's rare I even hear someone scraping a windscreen... i've only seen snow a few times here in 15 years.
So i went north. 10 miles north, and it was (according to car) -2.5 degrees. Left the gun under a bush and in the shade, bag open... scope temp strips said 2.5 an hour later... so had a go at ranging as it seemed like the temp would hold rather than warm up more.
At that temp i had 8 yds over-ranging. So 51.5 yds looked like 60. I don't have a 60 mark, but it was around there. But to qualify that, it's the same distance around the wheel as the hot shift... so actually it's the same 4mm as before, it's just that going the other way it was 8 yds.
My technique was to range on something I didn't know the distance of, and then run the tape. That way i wasn't convincing myself of something.
By the time i'd run the tape back, the scope had got up to 12 degrees and 14 was starting to light up... then the shift was about 1/2 that (which is what happens with the hot shift)... and then a few minutes later it was ranging on the money, 51.5 yds having hit 16+ on the temp strip. Heat haze was now a factor, and i was ranging into the low sun as well at a shadowed object, so really hard conditions, but still got a good hit on the range, good enough to send a pellet.
Gun was shooting about 5mm low... nothing to worry there.
Back out of there a couple of hours later, car was still saying 2.5 degrees above zero. So it shows you just how much the sun's rays can affect your scope.
10 miles south, i'm back in t-shirt weather again, 8 degrees.
So it looks like there's about 4mm either way on the wheel i have which makes 50-55 gaps about 5mm... something like that. It coincides roughly with a couple of marks on the pointer so i've got something to work with either way. Just need to pay attention to what temp she is and how long she's been there.
It's more than I thought at cold, but I still put 35 down at the weekend in cold conditions.