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Rifles, Reloading, Optics, Equipment
Rifles, Bullets, Barrels & Ballistics
Testing Friction Reduction of Bullet Coatings
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<blockquote data-quote="Michael Courtney" data-source="post: 682367" data-attributes="member: 28191"><p>You have some good insights. As bearing surface increases, friction usually increases also for the bullets we've tested. However, bullet construction is a bigger factor, and a solid copper bullet or a bullet with a steel core will usually have much more friction than a similar length jacketed lead bullet.</p><p></p><p>However, I would not think a lubricant would reduce friction by more than about the same percentage in a bullet with a longer bearing surface. It might be 12% of a bigger uncoated friction, therefore a bigger gain, but the percentage gain would be unlikely to be more than 12-15%. We've tested a lot of bullets with a lot of coatings and 15% is the best friction reduction we've ever seen.</p><p></p><p>For example, the 55 NBT lost 245 ft-lbs of energy to friction uncoated, and the 62 BFB (longer bearing surface) lost 330 ft-lbs of energy to friction uncoated. The coating of HBN reduced the friction by 15% and 12%, respectively. After these mediocre results, I've stopped coating my 140 AMAX (very long bearing surface) bullets in 6.5x284 and I've seen no negative results. </p><p></p><p> In fact, the testing we've done also shows that uncoated bullets have smaller shot-to-shot velocity variations. Not that coated bullets can't have impressive extreme spreads and standard deviations in velocity. In some cases they can. But in the bullet's we've tested, extreme spreads and standard deviations of uncoated bullets are consistently smaller.</p></blockquote><p></p>
[QUOTE="Michael Courtney, post: 682367, member: 28191"] You have some good insights. As bearing surface increases, friction usually increases also for the bullets we've tested. However, bullet construction is a bigger factor, and a solid copper bullet or a bullet with a steel core will usually have much more friction than a similar length jacketed lead bullet. However, I would not think a lubricant would reduce friction by more than about the same percentage in a bullet with a longer bearing surface. It might be 12% of a bigger uncoated friction, therefore a bigger gain, but the percentage gain would be unlikely to be more than 12-15%. We've tested a lot of bullets with a lot of coatings and 15% is the best friction reduction we've ever seen. For example, the 55 NBT lost 245 ft-lbs of energy to friction uncoated, and the 62 BFB (longer bearing surface) lost 330 ft-lbs of energy to friction uncoated. The coating of HBN reduced the friction by 15% and 12%, respectively. After these mediocre results, I've stopped coating my 140 AMAX (very long bearing surface) bullets in 6.5x284 and I've seen no negative results. In fact, the testing we've done also shows that uncoated bullets have smaller shot-to-shot velocity variations. Not that coated bullets can't have impressive extreme spreads and standard deviations in velocity. In some cases they can. But in the bullet's we've tested, extreme spreads and standard deviations of uncoated bullets are consistently smaller. [/QUOTE]
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Testing Friction Reduction of Bullet Coatings
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