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Rifles, Reloading, Optics, Equipment
Reloading
Help with velocity variance
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<blockquote data-quote="Striker77s" data-source="post: 454411" data-attributes="member: 28584"><p>All great comments, thanks again for your help. Clearly I need to move my Chrony back and try again. Unfortunately minutes after I finished the last test a snow storm moved in and dumped 8" of snow. So I won't be shooting for a while. I'll have to watch for any snow under the Chrony when I do finally make it to the range.</p><p></p><p>Boomtube: You are right in that fact that the delta in the gas temperature change is much larger than the initial temperature, hence the initial temperature gets lost in the noise. However I think the temperature impacts the powder burn rate which lasts up to 1ms. So it is a chemistry issue not a gas expansion issue. Which makes it much harder since I'm not a chemist. Each powder reacts differently to temperature variations. I chose Hodgdon 4831 since it is supposed to be temperature insensitive, but I've seen data from other shooters that suggest even temperature insensitive powder can vary the velocity at extreme temperatures. I wasn't thinking at the time but this is why my car heater experiment was flawed. Boss Hoss said that the cartridges have to be at ambient temperature for a while. I'm guessing it is because you aren't worried about the brass or air temperature but the powder temperature. It takes a while for the heat to flow to the powder even after the brass has been heated from a car heating vent.</p><p></p><p>WRG: Right now I'm more interested in long range target shooting. Eventually I would like to start shooting at 1000 yards but I'm still working on 300. I'm not happy with my loads yet to bother going to 1000. Quickloads looks very interesting, thanks for the tip.</p></blockquote><p></p>
[QUOTE="Striker77s, post: 454411, member: 28584"] All great comments, thanks again for your help. Clearly I need to move my Chrony back and try again. Unfortunately minutes after I finished the last test a snow storm moved in and dumped 8" of snow. So I won't be shooting for a while. I'll have to watch for any snow under the Chrony when I do finally make it to the range. Boomtube: You are right in that fact that the delta in the gas temperature change is much larger than the initial temperature, hence the initial temperature gets lost in the noise. However I think the temperature impacts the powder burn rate which lasts up to 1ms. So it is a chemistry issue not a gas expansion issue. Which makes it much harder since I'm not a chemist. Each powder reacts differently to temperature variations. I chose Hodgdon 4831 since it is supposed to be temperature insensitive, but I've seen data from other shooters that suggest even temperature insensitive powder can vary the velocity at extreme temperatures. I wasn't thinking at the time but this is why my car heater experiment was flawed. Boss Hoss said that the cartridges have to be at ambient temperature for a while. I'm guessing it is because you aren't worried about the brass or air temperature but the powder temperature. It takes a while for the heat to flow to the powder even after the brass has been heated from a car heating vent. WRG: Right now I'm more interested in long range target shooting. Eventually I would like to start shooting at 1000 yards but I'm still working on 300. I'm not happy with my loads yet to bother going to 1000. Quickloads looks very interesting, thanks for the tip. [/QUOTE]
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Rifles, Reloading, Optics, Equipment
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Help with velocity variance
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