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Rifles, Reloading, Optics, Equipment
Rifles, Bullets, Barrels & Ballistics
AR-50 Velocity. I need to know what velocity i should be getting with my new AR-50 50 BMG
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<blockquote data-quote="Rifleman97" data-source="post: 2084197" data-attributes="member: 103996"><p>As for powders the old 872 is gone, however US 869 is basically the replacement for it. For velocity, you'll lose around 11-30fps for every inch of barrel length under 36 inches. The closer to 36 being the less amount lost. For example </p><p>35" would be 11fps lost</p><p>34" would be 13fps lost</p><p>33" would be 15fps lost</p><p>32" would be 18fps lost</p><p>all of those numbers being compounding, assuming the use of US 869. Which is not super temp stable, however it's what comes with most powders suitable for the 50.</p><p></p><p>On top of that, the temp you're shooting at fan widely change the velocity. Hodgdon lists US 869 as losing or gaining 1.5fps on standard rounds (so possibly more for you) per degree under 75°. So if you are shooting in 30° weather you're losing at least 67.5 FPS just from the temp alone. And most slow burning powders (like 50BMG, and other powders meant for the 50) are similarly temp unstable. Combine that with what is lost with your 30" barrel and you should be in the 2450(worst case) to 2570fps (best case) range assuming 750gr bullet and US 869 at around 30°F. 2400 would not be out of the question but does seem a bit low, however using a bullet with a larger bearing surface could account for such a low velocity.</p></blockquote><p></p>
[QUOTE="Rifleman97, post: 2084197, member: 103996"] As for powders the old 872 is gone, however US 869 is basically the replacement for it. For velocity, you’ll lose around 11-30fps for every inch of barrel length under 36 inches. The closer to 36 being the less amount lost. For example 35” would be 11fps lost 34” would be 13fps lost 33” would be 15fps lost 32” would be 18fps lost all of those numbers being compounding, assuming the use of US 869. Which is not super temp stable, however it’s what comes with most powders suitable for the 50. On top of that, the temp you’re shooting at fan widely change the velocity. Hodgdon lists US 869 as losing or gaining 1.5fps on standard rounds (so possibly more for you) per degree under 75°. So if you are shooting in 30° weather you’re losing at least 67.5 FPS just from the temp alone. And most slow burning powders (like 50BMG, and other powders meant for the 50) are similarly temp unstable. Combine that with what is lost with your 30” barrel and you should be in the 2450(worst case) to 2570fps (best case) range assuming 750gr bullet and US 869 at around 30°F. 2400 would not be out of the question but does seem a bit low, however using a bullet with a larger bearing surface could account for such a low velocity. [/QUOTE]
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AR-50 Velocity. I need to know what velocity i should be getting with my new AR-50 50 BMG
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