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Rifles, Reloading, Optics, Equipment
AR15/10 Rifles
What learned over time building AR's
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<blockquote data-quote="budlight" data-source="post: 3092104" data-attributes="member: 2939"><p>Barrel twist rate is just a number like one rotation for every 7 inches of barrel. Let's then max pressure load 40 gr .224 and 80 grain pills out of a 20 inch barrel .223. The 40 grain comes out of a 20 inch barrel at approximatley 3700 fps and the 80 clear down at 2700 fps.</p><p></p><p>The same barrel and same twist rate. The faster 40 grain will have a much higher RPM spin rate than the slower 80 grain. You can actually find the calculated spin rate formulas online. That is why longer heavy per caliber bullets require faster twist rate barrels to achieve stability in flight. They are going slower.</p><p></p><p>Over rpm a bullet and it no longer has a stable flight. It has Yaw and Pitch angles that cause it to fly sideways through a 50 yard sight in target. I was splattering the target with pie plate sized patterns.</p></blockquote><p></p>
[QUOTE="budlight, post: 3092104, member: 2939"] Barrel twist rate is just a number like one rotation for every 7 inches of barrel. Let's then max pressure load 40 gr .224 and 80 grain pills out of a 20 inch barrel .223. The 40 grain comes out of a 20 inch barrel at approximatley 3700 fps and the 80 clear down at 2700 fps. The same barrel and same twist rate. The faster 40 grain will have a much higher RPM spin rate than the slower 80 grain. You can actually find the calculated spin rate formulas online. That is why longer heavy per caliber bullets require faster twist rate barrels to achieve stability in flight. They are going slower. Over rpm a bullet and it no longer has a stable flight. It has Yaw and Pitch angles that cause it to fly sideways through a 50 yard sight in target. I was splattering the target with pie plate sized patterns. [/QUOTE]
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AR15/10 Rifles
What learned over time building AR's
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