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<blockquote data-quote="ta406" data-source="post: 1330545" data-attributes="member: 34644">So I&#039;m in the process of developing a load for a new custom 300 WM. It has a fluted, medium palma 28&quot; bartlein barrel. I&#039;m testing 215 bergers and VV N570 powder. It was 80 degrees and sunny during testing. I shot 3 groups of 4 rounds each. Each group, the powder charge was increased by .5 grains. My testing went like this. Fire 2 rounds, cool the barrel with a small air mattress pump, then fire the next two rounds. After the third group, I noticed that the first round was about 30fps faster than the second. Then the third was 20-30fps faster than the second. Then the forth was 20 or so fps slower than the third. Something like this:1) 30002) 2970barrel cool down3) 29904) 2965This trend was consistent with all three groups that I fired. As you can see that my ES was horrible and got me thinking as how, or if I can do any type of load development with this rifle in warmer weather. I have never had this issue with any of my other rifles. I guess for load development, I will have to let the barrel cool completely between each shot.&nbsp; But now I&#039;m also questioning how confident I will be using this rifle if I have to take a follow up shot or two at extended ranges in hunting conditions.&nbsp; I was going to test H1000 this weekend to see if the trend continues even with a different powder. I will keep all other components the same. Has anyone ran into a similar problem?</blockquote>

[QUOTE="ta406, post: 1330545, member: 34644"] So I'm in the process of developing a load for a new custom 300 WM. It has a fluted, medium palma 28" bartlein barrel. I'm testing 215 bergers and VV N570 powder. It was 80 degrees and sunny during testing. I shot 3 groups of 4 rounds each. Each group, the powder charge was increased by .5 grains. My testing went like this. Fire 2 rounds, cool the barrel with a small air mattress pump, then fire the next two rounds. After the third group, I noticed that the first round was about 30fps faster than the second. Then the third was 20-30fps faster than the second. Then the forth was 20 or so fps slower than the third. Something like this: 1) 3000 2) 2970 barrel cool down 3) 2990 4) 2965 This trend was consistent with all three groups that I fired. As you can see that my ES was horrible and got me thinking as how, or if I can do any type of load development with this rifle in warmer weather. I have never had this issue with any of my other rifles. I guess for load development, I will have to let the barrel cool completely between each shot. But now I'm also questioning how confident I will be using this rifle if I have to take a follow up shot or two at extended ranges in hunting conditions. I was going to test H1000 this weekend to see if the trend continues even with a different powder. I will keep all other components the same. Has anyone ran into a similar problem? [/QUOTE]

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