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Rifles, Reloading, Optics, Equipment
Reloading
300 RUM, 240 SMK, US869 Initial Results
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<blockquote data-quote="Jon A" data-source="post: 114433" data-attributes="member: 319"><p>Some more data. While it wasn't my intention to conduct a scientific test of temp stability (or I obviously would have kept everything the same), I did want to double check the 103 grain load in warm weather (it was about 20 degrees warmer this time than last time I chronoed them) but I also changed the seating depth by .020". So the difference could have come from either one or a combination of both. Anyway, here are the final results:</p><p></p><p>I ran six rounds over the chronograph at 103 grains. Average was 3031, which is <em>a bit hot.</em> Those that were at or under that <em>average</em> probably wouldn't be a problem. It's those that are over that are. A couple were over 3050 which is obviously too hot. But here's the worst part--in both three shot groups, two landed in under 1/4 MOA. But in each case, the round that chronographed the highest was a flier about 1 MOA from the first two--which is what one would expect when the pressure gets that high.</p><p></p><p>Since I'll stick to this seating depth and most of my shooting this summer will be at 85+ degrees, I'm going to knock that load down two full grains, to 101. That should put me in the 2970-2980 range (at 80 degrees at least) and give me a nice healthy margin for hot days. </p><p></p><p>Keep in mind, I never expected this powder to be 100% temp insensitive (I still can't say with any certainty that it's not), just better than H870 and WC872 (which isn't too difficult). But I think using some common sense as the summer heats up is probably a good call until proven otherwise.</p><p></p><p>Also keep in mind H50BMG would have been popping primers at those velocities...and Retumbo likely would have been blowing cases. And neither of those is 100% temp insensitive either. So, I still feel US 869 is working perfectly for this application. Nothing else comes close.</p></blockquote><p></p>
[QUOTE="Jon A, post: 114433, member: 319"] Some more data. While it wasn't my intention to conduct a scientific test of temp stability (or I obviously would have kept everything the same), I did want to double check the 103 grain load in warm weather (it was about 20 degrees warmer this time than last time I chronoed them) but I also changed the seating depth by .020". So the difference could have come from either one or a combination of both. Anyway, here are the final results: I ran six rounds over the chronograph at 103 grains. Average was 3031, which is [i]a bit hot.[/i] Those that were at or under that [i]average[/i] probably wouldn't be a problem. It's those that are over that are. A couple were over 3050 which is obviously too hot. But here's the worst part--in both three shot groups, two landed in under 1/4 MOA. But in each case, the round that chronographed the highest was a flier about 1 MOA from the first two--which is what one would expect when the pressure gets that high. Since I'll stick to this seating depth and most of my shooting this summer will be at 85+ degrees, I'm going to knock that load down two full grains, to 101. That should put me in the 2970-2980 range (at 80 degrees at least) and give me a nice healthy margin for hot days. Keep in mind, I never expected this powder to be 100% temp insensitive (I still can't say with any certainty that it's not), just better than H870 and WC872 (which isn't too difficult). But I think using some common sense as the summer heats up is probably a good call until proven otherwise. Also keep in mind H50BMG would have been popping primers at those velocities...and Retumbo likely would have been blowing cases. And neither of those is 100% temp insensitive either. So, I still feel US 869 is working perfectly for this application. Nothing else comes close. [/QUOTE]
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Rifles, Reloading, Optics, Equipment
Reloading
300 RUM, 240 SMK, US869 Initial Results
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