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Rifles, Reloading, Optics, Equipment
Reloading
Pressure signs/chronographing
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<blockquote data-quote=".280Rem" data-source="post: 205277" data-attributes="member: 11140"><p>The simple answer is that velocity is the single greatest indicator of pressure that we have without using pressure testing equipment. </p><p> </p><p>Here's the best way I know to describe it. The manufactures work up their data to SAAMI pressure specs, and in fact, usually stay about 2-3K psi under SAAMI max. I'll tell you how I work up my loads. I'll use the 30-06 as an example. I look up data from several sources. I like Nosler data, and Alliant powder seems to be good for me too. Alliant says 60 grs R-22 and a 165 Nosler Partiton get 2755 in a 24" bbl at 51K psi. Nosler says that same powder charge gets 2850. It doesn't give a pressure, but they're loading right up to 60K psi, and they say max is 63grs at 3002fps. (Some would say this is hot) So, at the same powder charge with the same bullet, you got a 100fps difference. Well, looking at most data you'll find that most max velocity given for most 165 bullets will top out around 2850-2950. So, with R-22, you start working up from say 57 grains, and when you hit that velocity range (assuming a like legth bbl), you've found your max load. Slower powders give better velocity with less pressure. If you went with H4350, then you might top out on the low end of that velocity range. In my experience, you can't get enough R-22 in the 30-06 with 165s to do any damage or even get pressure signs. In my 30-06 with a 23.6" bbl 60grs of R-22 and a 165 Hornady gets 2875. I shoot as my hunting load 57.5 grs of H4350 and 165 Accubonds at 2850. Some say 58.0 grs is max at that velocity. I'm sure I could go another half or even up to 58.5, but I'm where I want to be. The faster the burn rate of the powder, the quicker your pressure will rise, and you'll get higher pressures at lower velocities. Study all the data and you'll see the trends. To me the "max load listed" is the max velocity with the given powder. If I reach the max powder charge listed but am 200fps slower than the velocity listed...I'll add more powder. If I hit max velocity 1 or 2 grains short of the max powder charge, then I quit there. Velocity = pressure, but you have to factor in powder burn rate. 2850 with a 165 will give vastly different pressures with R-15, R-19 and R-22. I'd speculate you might not be able to safely reach 2850 with R-15. With R-22, you'd be at a VERY low pressure, some 9K psi short of SAAMI max according to Alliant. </p><p> </p><p>These two links show the burn rate vs. velocity vs. pressure, and also show how different bullets, because of their bearing surface, can affect pressure too.</p><p> </p><p>Learn to <em>really</em> read the data and look beyond what the "max listed powder charge" is and apply common sense, and you'll be fine. That new chrony is a valuable tool in reloading. </p><p> </p><p><a href="http://www.alliantpowder.com/reloaders/RecipeDetail.aspx?title=Centerfire%20Load&gtypeid=2&weight=165&shellid=1071&bulletid=257" target="_blank">Reloading Data</a></p><p> </p><p><a href="http://www.alliantpowder.com/reloaders/RecipeDetail.aspx?title=Centerfire%20Load&gtypeid=2&weight=165&shellid=1071&bulletid=258" target="_blank">Reloading Data</a></p></blockquote><p></p>
[QUOTE=".280Rem, post: 205277, member: 11140"] The simple answer is that velocity is the single greatest indicator of pressure that we have without using pressure testing equipment. Here's the best way I know to describe it. The manufactures work up their data to SAAMI pressure specs, and in fact, usually stay about 2-3K psi under SAAMI max. I'll tell you how I work up my loads. I'll use the 30-06 as an example. I look up data from several sources. I like Nosler data, and Alliant powder seems to be good for me too. Alliant says 60 grs R-22 and a 165 Nosler Partiton get 2755 in a 24" bbl at 51K psi. Nosler says that same powder charge gets 2850. It doesn't give a pressure, but they're loading right up to 60K psi, and they say max is 63grs at 3002fps. (Some would say this is hot) So, at the same powder charge with the same bullet, you got a 100fps difference. Well, looking at most data you'll find that most max velocity given for most 165 bullets will top out around 2850-2950. So, with R-22, you start working up from say 57 grains, and when you hit that velocity range (assuming a like legth bbl), you've found your max load. Slower powders give better velocity with less pressure. If you went with H4350, then you might top out on the low end of that velocity range. In my experience, you can't get enough R-22 in the 30-06 with 165s to do any damage or even get pressure signs. In my 30-06 with a 23.6" bbl 60grs of R-22 and a 165 Hornady gets 2875. I shoot as my hunting load 57.5 grs of H4350 and 165 Accubonds at 2850. Some say 58.0 grs is max at that velocity. I'm sure I could go another half or even up to 58.5, but I'm where I want to be. The faster the burn rate of the powder, the quicker your pressure will rise, and you'll get higher pressures at lower velocities. Study all the data and you'll see the trends. To me the "max load listed" is the max velocity with the given powder. If I reach the max powder charge listed but am 200fps slower than the velocity listed...I'll add more powder. If I hit max velocity 1 or 2 grains short of the max powder charge, then I quit there. Velocity = pressure, but you have to factor in powder burn rate. 2850 with a 165 will give vastly different pressures with R-15, R-19 and R-22. I'd speculate you might not be able to safely reach 2850 with R-15. With R-22, you'd be at a VERY low pressure, some 9K psi short of SAAMI max according to Alliant. These two links show the burn rate vs. velocity vs. pressure, and also show how different bullets, because of their bearing surface, can affect pressure too. Learn to [I]really[/I] read the data and look beyond what the "max listed powder charge" is and apply common sense, and you'll be fine. That new chrony is a valuable tool in reloading. [URL="http://www.alliantpowder.com/reloaders/RecipeDetail.aspx?title=Centerfire%20Load>ypeid=2&weight=165&shellid=1071&bulletid=257"]Reloading Data[/URL] [URL="http://www.alliantpowder.com/reloaders/RecipeDetail.aspx?title=Centerfire%20Load>ypeid=2&weight=165&shellid=1071&bulletid=258"]Reloading Data[/URL] [/QUOTE]
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