goodgrouper
Well-Known Member
I was drumming out the best load I could find for a new 6br improved barrel this week and had an interesting discovery. A few days ago, I was shooting in absolutely frigid conditions out in the desert with some Varget and some RL15. I don't know how cold it was but Coke froze solid in about an hour. And I mean solid. I found a load with RL15 that shot a .3" at 100 yards and then 4.25" at 900 yards. The speed was 3035 on the 95 grain VLD. Varget had bad deviations to the point where I believed my bottle had somehow gotten spoiled. The best load was going 3110 fps and had an SD of 10. MOst of the SD's were in the 30's!!!! This is not normal for a 6br improved with Varget.
Today, I'm in the same place, shooting the same gun, same powder, same primers and all. But the temp was 40 degrees. The exact same loads today were between 60 and 110 fps faster with dang near identical standard deviations to the freezing weather deviations! I have never seen this much jump in velocity--especially for Varget.
Then to compound the confusion, I loaded up a same charge of Varget as the above load only this was a different lot. It was 5 fps off the first lot but the SD was 3 fps!!! So apparently, the first lot of Varget won't work but the other lot will. Very unnerving.
RL15 kept it's good SD's both days but the velocity increase was severe enough to bump me out of the node. I had to back down 1.5 grains to get it back down where it shot small groups.
So, I'm guessing the temp difference was 25 degrees in the two days and that would normally be easy to tune for. But something about the bitter cold changed things significantly. Perhaps, fine tuning a competition rifle isn't a good idea when the Coke in the bottle freezes in front of your eyes!? Anyhow, I'm going to wait until it warms up a bit before doing any more work on this one.
Today, I'm in the same place, shooting the same gun, same powder, same primers and all. But the temp was 40 degrees. The exact same loads today were between 60 and 110 fps faster with dang near identical standard deviations to the freezing weather deviations! I have never seen this much jump in velocity--especially for Varget.
Then to compound the confusion, I loaded up a same charge of Varget as the above load only this was a different lot. It was 5 fps off the first lot but the SD was 3 fps!!! So apparently, the first lot of Varget won't work but the other lot will. Very unnerving.
RL15 kept it's good SD's both days but the velocity increase was severe enough to bump me out of the node. I had to back down 1.5 grains to get it back down where it shot small groups.
So, I'm guessing the temp difference was 25 degrees in the two days and that would normally be easy to tune for. But something about the bitter cold changed things significantly. Perhaps, fine tuning a competition rifle isn't a good idea when the Coke in the bottle freezes in front of your eyes!? Anyhow, I'm going to wait until it warms up a bit before doing any more work on this one.
