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Rifles, Reloading, Optics, Equipment
Rifles, Bullets, Barrels & Ballistics
7mm Allen Mag test rifle finished.....
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<blockquote data-quote="ricka0" data-source="post: 76224" data-attributes="member: 3086"><p><strong>wc872 burn rate</strong></p><p></p><p>[ QUOTE ]</p><p><font color="purple"> b1g b0re the H-50 BMG powder works great in my RUM but heats the barrel very fast! The wc872 Kirby is using burns slower than the H-50 BMG and cooler from his testing and mine. </font> </p><p></p><p>[/ QUOTE ] </p><p></p><p>There has been a lot of talk about some powders burning hotter than others, but it's all silly talk. The only thing that accelerates a bullet is good old <font color="brown"> <strong>PV=nRT </strong> </font> from hi-skoul chemistry <a href="http://scienceworld.wolfram.com/physics/IdealGasLaw.html" target="_blank">Ideal Gas Law </a></p><p> <strong>P</strong>ressure * <strong>V</strong>olume = <strong>n</strong> (# of atoms) * <strong>R</strong> (universal gas constant) * <strong>T</strong> emperature.</p><p></p><p>Pressure: [*]Volume is fixed (chamber/barrel) [*]# of atoms fixed (new gas molecules contribute &lt; 1%) [*]R is constant</p><p></p><p>So there is a direct relationship between temp and pressure. You cannot have lower temp without having lower pressure. Pressure is simply the Force in F=MA or A = F/M (acceleration = Force/mass). Any mathematician worth her salt would tell you what counts in the integral of the pressure curve - which looks like</p><p> <img src="http://www.shootingsoftware.com/images/sampletrace1.gif" alt="" class="fr-fic fr-dii fr-draggable " style="" /></p><p></p><p>I show this to rule out a Dirac delta function which could transfer less heat to the barrel while producing higher velocity. Generally Dirac spike conditions (when your engine pings) produce <font color="red"><strong> <em>far less</em> </font> </strong> acceleration.</p><p></p><p>If anyone has any empirical data on barrel temp vs. velocity with different powders I'd like to see it. You can get a lower velocity and a hotter barrel by burning a slow powder (H-50BMG) in a short barrel - where much of the powder burns after the bullet leaves the barrel (and thus contributes only to heating the barrel, not accelerating the bullet) - but in that case you have selected the wrong powder.</p><p></p><p>[ QUOTE ]</p><p><font color="purple"> The wc872 Kirby is using burns <font color="red"> <strong>slower</strong> </font> than the H-50 BMG </font> </p><p></p><p>[/ QUOTE ] </p><p>WC872 is 20mm Vulcan ball powder which can be loaded using Hodgdon H870 or AA8700 data. You can get it from <a href="https://protected.imoutdoorshosting.com/gibrass/gunpowder.html" target="_blank">Jeff Bartlett for only $40/8 lbs (what a bargain!)</a> </p><p>A slower burning powder producing equivalent velocity <strong>can <em>ONLY</em> </strong> result in a hotter barrel. So you're probably right about your barrel getting hotter, the H50BMG burns slower (and incompletely) producing a <strong> <em>slightly</em> </strong> hotter barrel - but apparently wrong about the relative rates. Given heat transfer is proportional to Temp/area (which is const) and time - I doubt you could measure the barrel temperature difference (given they produced identical velocities).</p><p></p><p>Burn Rates: (fastest to slowest)</p><p>10 Bullseye (Alliant) </p><p>17 Red Dot (Alliant) </p><p></p><p>122 N120 (Vihtavuori) </p><p>123 4227 (IMR) </p><p></p><p>209 N150 (Vihtavuori) </p><p>210 N550 (Vihtavuori) </p><p>211 4350 XMR (Accurate) </p><p><strong> <font color="red"> 212 4350 (IMR)</strong></font> -------------- // ricka's favorite hunting rifle powder </p><p>216 H4350 (Hodgdon) </p><p></p><p>242 7828 (IMR) </p><p>243 H1000 (Hodgdon) </p><p>248 Reloader 25 (Alliant) </p><p></p><p>252 Retumbo (Hodgdon) </p><p> <font color="red"> <strong>254 H870</strong> </font> (Hodgdon)-------------- same as wc872 </p><p>... </p><p></p><p><font color="red"><strong>259 8700</font></strong> (Accurate)------------- same as wc872 </p><p>260 24N41 (Vihtavuori) </p><p>261 W870 (Winchester) </p><p> <font color="purple"> <strong>262 50 BMG </strong> </font> (Hodgdon) ----------- reference data 50 BMG </p><p>263 H5010 (Hodgdon) </p><p>264 PCL 513 (PB Clermont) </p><p>265 </p><p>266 20N29 (Vihtavuori) </p><p>see <a href="http://groups.msn.com/50bmg/vihtavuori20n29loads.msnw" target="_blank">B1g_B0re's powder page</a> for burn rate comparisons.</p></blockquote><p></p>
[QUOTE="ricka0, post: 76224, member: 3086"] [b]wc872 burn rate[/b] [ QUOTE ] <font color="purple"> b1g b0re the H-50 BMG powder works great in my RUM but heats the barrel very fast! The wc872 Kirby is using burns slower than the H-50 BMG and cooler from his testing and mine. </font> [/ QUOTE ] There has been a lot of talk about some powders burning hotter than others, but it's all silly talk. The only thing that accelerates a bullet is good old <font color="brown"> [b]PV=nRT [/b] </font> from hi-skoul chemistry [url="http://scienceworld.wolfram.com/physics/IdealGasLaw.html"]Ideal Gas Law [/url] [b]P[/b]ressure * [b]V[/b]olume = [b]n[/b] (# of atoms) * [b]R[/b] (universal gas constant) * [b]T[/b] emperature. Pressure: [*]Volume is fixed (chamber/barrel) [*]# of atoms fixed (new gas molecules contribute < 1%) [*]R is constant So there is a direct relationship between temp and pressure. You cannot have lower temp without having lower pressure. Pressure is simply the Force in F=MA or A = F/M (acceleration = Force/mass). Any mathematician worth her salt would tell you what counts in the integral of the pressure curve - which looks like [img]http://www.shootingsoftware.com/images/sampletrace1.gif[/img] I show this to rule out a Dirac delta function which could transfer less heat to the barrel while producing higher velocity. Generally Dirac spike conditions (when your engine pings) produce <font color="red">[b] [i]far less[/i] </font> [/b] acceleration. If anyone has any empirical data on barrel temp vs. velocity with different powders I'd like to see it. You can get a lower velocity and a hotter barrel by burning a slow powder (H-50BMG) in a short barrel - where much of the powder burns after the bullet leaves the barrel (and thus contributes only to heating the barrel, not accelerating the bullet) - but in that case you have selected the wrong powder. [ QUOTE ] <font color="purple"> The wc872 Kirby is using burns <font color="red"> [b]slower[/b] </font> than the H-50 BMG </font> [/ QUOTE ] WC872 is 20mm Vulcan ball powder which can be loaded using Hodgdon H870 or AA8700 data. You can get it from [url="https://protected.imoutdoorshosting.com/gibrass/gunpowder.html"]Jeff Bartlett for only $40/8 lbs (what a bargain!)[/url] A slower burning powder producing equivalent velocity [b]can [i]ONLY[/i] [/b] result in a hotter barrel. So you're probably right about your barrel getting hotter, the H50BMG burns slower (and incompletely) producing a [b] [i]slightly[/i] [/b] hotter barrel - but apparently wrong about the relative rates. Given heat transfer is proportional to Temp/area (which is const) and time - I doubt you could measure the barrel temperature difference (given they produced identical velocities). Burn Rates: (fastest to slowest) 10 Bullseye (Alliant) 17 Red Dot (Alliant) 122 N120 (Vihtavuori) 123 4227 (IMR) 209 N150 (Vihtavuori) 210 N550 (Vihtavuori) 211 4350 XMR (Accurate) [b] <font color="red"> 212 4350 (IMR)[/b]</font> -------------- // ricka's favorite hunting rifle powder 216 H4350 (Hodgdon) 242 7828 (IMR) 243 H1000 (Hodgdon) 248 Reloader 25 (Alliant) 252 Retumbo (Hodgdon) <font color="red"> [b]254 H870[/b] </font> (Hodgdon)-------------- same as wc872 ... <font color="red">[b]259 8700</font>[/b] (Accurate)------------- same as wc872 260 24N41 (Vihtavuori) 261 W870 (Winchester) <font color="purple"> [b]262 50 BMG [/b] </font> (Hodgdon) ----------- reference data 50 BMG 263 H5010 (Hodgdon) 264 PCL 513 (PB Clermont) 265 266 20N29 (Vihtavuori) see [url="http://groups.msn.com/50bmg/vihtavuori20n29loads.msnw"]B1g_B0re's powder page[/url] for burn rate comparisons. [/QUOTE]
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