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Extreme Long Range Hunting & Shooting (ELR)
"High" pressure vs "Standard" pressure
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<blockquote data-quote="J E Custom" data-source="post: 1313593" data-attributes="member: 2736"><p>All good questions and I will try to answer in my opinion.</p><p></p><p>As I stated earlier, When we abide by the pressure limits set By SAMMI all things seem to work well</p><p>without failure. As discussed Brass is the week link with standard factory chambers or poorly cut custom chambers. With a good chamber design and careful loading most cases will operate above 65,000 PSI although shorter life can be expected. when brass is pushed to 70,000 PSI life will become short and other issues start to show up.</p><p></p><p>Powders create gas that creates pressure and that Is the reason we have so many different burn rates. Powders produce the same volume of gas for the same amount weight depending on whether</p><p>it is single base powder or double based powder. But change the pressure peak based of burn rates for the same amount of powder. So If you go with a slower burning powder and more volume and can use more grains of powder it will produce more gas by volume with no more pressure . As long as the barrel can utilize the extra powder, velocity will increase with no higher peak pressure.</p><p></p><p>There are other chamber dimensions that can increase velocity without increasing pressure.</p><p></p><p>Many years ago pressures were held to mid to high 40,000 PSIs of pressures because of the metallurgy and not the brass. As designs improved and the metallurgy got better and more consistent, the pressure standard was increased in modern firearms to 55,000. Now with some cartridge designs the pressure will safely handle 70,000 psi but brass will not survive very long</p><p>so we have reached the brass limit. On these cartridges barrel shank diameter becomes an issue because of expansion during firing. The chamber expands allowing the brass to expand but the chamber returns to its original dimension because it did not reach yield, but the brass does and the chamber compresses the brass making it hard to extract.(Heavy bolt lift).</p><p></p><p>I have many examples of increasing the powder charge and capacity with no increase in pressure but much more velocity. and these changes were more than One change. It takes many subtle change to push a 300 grain .338 bullet to 3,150 starting with a 300 rum size case and prevent heavy bolt lift. (Excessive pressure).</p><p></p><p>I am all for advancing the sport through innovation, but at some point you have to ask, is it worth the problems and cost.</p><p></p><p>Just my opinion</p><p></p><p>J E CUSTOM</p></blockquote><p></p>
[QUOTE="J E Custom, post: 1313593, member: 2736"] All good questions and I will try to answer in my opinion. As I stated earlier, When we abide by the pressure limits set By SAMMI all things seem to work well without failure. As discussed Brass is the week link with standard factory chambers or poorly cut custom chambers. With a good chamber design and careful loading most cases will operate above 65,000 PSI although shorter life can be expected. when brass is pushed to 70,000 PSI life will become short and other issues start to show up. Powders create gas that creates pressure and that Is the reason we have so many different burn rates. Powders produce the same volume of gas for the same amount weight depending on whether it is single base powder or double based powder. But change the pressure peak based of burn rates for the same amount of powder. So If you go with a slower burning powder and more volume and can use more grains of powder it will produce more gas by volume with no more pressure . As long as the barrel can utilize the extra powder, velocity will increase with no higher peak pressure. There are other chamber dimensions that can increase velocity without increasing pressure. Many years ago pressures were held to mid to high 40,000 PSIs of pressures because of the metallurgy and not the brass. As designs improved and the metallurgy got better and more consistent, the pressure standard was increased in modern firearms to 55,000. Now with some cartridge designs the pressure will safely handle 70,000 psi but brass will not survive very long so we have reached the brass limit. On these cartridges barrel shank diameter becomes an issue because of expansion during firing. The chamber expands allowing the brass to expand but the chamber returns to its original dimension because it did not reach yield, but the brass does and the chamber compresses the brass making it hard to extract.(Heavy bolt lift). I have many examples of increasing the powder charge and capacity with no increase in pressure but much more velocity. and these changes were more than One change. It takes many subtle change to push a 300 grain .338 bullet to 3,150 starting with a 300 rum size case and prevent heavy bolt lift. (Excessive pressure). I am all for advancing the sport through innovation, but at some point you have to ask, is it worth the problems and cost. Just my opinion J E CUSTOM [/QUOTE]
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"High" pressure vs "Standard" pressure
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