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Rifles, Reloading, Optics, Equipment
Rifles, Bullets, Barrels & Ballistics
Your input desired on design of barrel friction experiment with bullet coatings
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<blockquote data-quote="Michael Courtney" data-source="post: 565573" data-attributes="member: 28191"><p>We have thought this out carefully.</p><p></p><p>The next step is quantifying how much friction is reduced by a given coating. If energy loss to friction can be reduced from 200 ft-lbs to 100 ft-lbs in a given cartridge, then increasing the powder charge (or possibly using a different powder) should be able to increase the muzzle energy by 100 ft-lbs with the same peak pressure and cartridge. If energy loss can be reduced from 1000 ft-lbs to 500 ft-lbs then the energy should be able to be increased by 500 ft-lbs for the same bullet and cartridge and peak pressure. </p><p></p><p>Why hasn't this already been done? I can think of several possibilities. Perhaps no one has had the tools to accurately quantify barrel friction with and without coatings. We have that now. Perhaps there are more commercial gains to be had in introducing new cartridges rather than making the old ones work better. I suspect that reliable gains in friction reduction through coatings require more control over barrel quality and cleaning than can be exercised by an ammunition supplier, so they are reluctant to load ammo much hotter lest a small percentage of pitted or rusty barrels lead to a lot of liability lawsuits.</p><p></p><p>Another fact to consider is that barrel friction will be highly correlated with fouling. (What other than friction rubs the copper from the bullet?) Fouling is a challenge to quantify, but now friction can be accurately quantified. A coating that does the best job at reducing barrel friction will most likely also do the best job reducing barrel fouling because it will reduce the forces between barrel and bullet which are rubbing the copper from the bullet.</p><p></p><p>We've worked a bit with sabots and the energy lost to friction with a saboted load can pretty easily be reduced to about 80 ft-lbs. However, maintaining the accuracy needed for reliable hits beyond 200 yards is much harder than with coated bullets. In addition, sabots are a custom deal in all but a few calibers.</p><p></p><p>Is a 100 to 500 ft-lb gain enough to justify a given coating? It depends on the application. Some match shooters need to stretch the .308 Win or .223 Rem to longer distances, and it might be. I could certainly use 500 ft-lbs more in my long range rigs in 25-06, 6.5x284, and .300 Win Mag, and I'd much rather get the gain from a bullet coating than rebarreling.</p></blockquote><p></p>
[QUOTE="Michael Courtney, post: 565573, member: 28191"] We have thought this out carefully. The next step is quantifying how much friction is reduced by a given coating. If energy loss to friction can be reduced from 200 ft-lbs to 100 ft-lbs in a given cartridge, then increasing the powder charge (or possibly using a different powder) should be able to increase the muzzle energy by 100 ft-lbs with the same peak pressure and cartridge. If energy loss can be reduced from 1000 ft-lbs to 500 ft-lbs then the energy should be able to be increased by 500 ft-lbs for the same bullet and cartridge and peak pressure. Why hasn't this already been done? I can think of several possibilities. Perhaps no one has had the tools to accurately quantify barrel friction with and without coatings. We have that now. Perhaps there are more commercial gains to be had in introducing new cartridges rather than making the old ones work better. I suspect that reliable gains in friction reduction through coatings require more control over barrel quality and cleaning than can be exercised by an ammunition supplier, so they are reluctant to load ammo much hotter lest a small percentage of pitted or rusty barrels lead to a lot of liability lawsuits. Another fact to consider is that barrel friction will be highly correlated with fouling. (What other than friction rubs the copper from the bullet?) Fouling is a challenge to quantify, but now friction can be accurately quantified. A coating that does the best job at reducing barrel friction will most likely also do the best job reducing barrel fouling because it will reduce the forces between barrel and bullet which are rubbing the copper from the bullet. We've worked a bit with sabots and the energy lost to friction with a saboted load can pretty easily be reduced to about 80 ft-lbs. However, maintaining the accuracy needed for reliable hits beyond 200 yards is much harder than with coated bullets. In addition, sabots are a custom deal in all but a few calibers. Is a 100 to 500 ft-lb gain enough to justify a given coating? It depends on the application. Some match shooters need to stretch the .308 Win or .223 Rem to longer distances, and it might be. I could certainly use 500 ft-lbs more in my long range rigs in 25-06, 6.5x284, and .300 Win Mag, and I'd much rather get the gain from a bullet coating than rebarreling. [/QUOTE]
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Your input desired on design of barrel friction experiment with bullet coatings
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