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Rifles, Reloading, Optics, Equipment
Rifles, Bullets, Barrels & Ballistics
Custom action pressure ceiling.
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<blockquote data-quote="LouBoyd" data-source="post: 375223" data-attributes="member: 9253"><p>Perhaps I misunderstood Rocky's question . To determine what load and bullet gives what pressure in a wildcat cartridge the computer Program Quickload is quite helpful. To use it however you need to use bullets and powders which are in Quickload's database. The case capacity, neck diameter and case length are minimum information about the case and chamber. As a first approximation with the the powder type, case capacity, bullet type (including jacket material, mass, and length) bullet seating depth, and barrel length you can predict what velocity your load should have vs chamber pressure. Freebore is not part of Quickloads calculation, nor is primer energy. </p><p>Combining the information from Quckloads calculation with actual bullet velocity measured by a chronograph will give a good estimate of the pressure curve in chamber of a wildcat cartridge. There are at least six parameters which define how a powder burns. Just guessing that the powder you're using is similar to a powder which is in the database can lead to very wrong estimates of the pressure curves even though the two powders might give the same velocity. </p><p></p><p>There are also commercial strain gauge kits which can be fitted to most rifle actions to measure the chamber pressure curve directly. Accurate dimension of the chamber wall thickness needs to be knows as does the modulus of elasticity of the alloy the chamber is made of. When a rifle is fired the outside wall of the receiver expands linearly with internal pressure as long as the elastic limit of the receiver isn't exceeded, which it wont be for normal cartridge pressures. The strain gage measures how much the barrel stretches vs time when fired and a relative simple formula then calculates the pressure curve. From the pressure curve and the cartridge dimension the forces on the receiver and bolt can be determined. </p><p> </p><p>As to what the design maximum pressure for a given receiver might be that should be obtained from the receiver's designer and manufacturer. Hopefully the designer did thorough calculations and the manufacturer followed the design, particularly with the metallurgy and heat treating.</p></blockquote><p></p>
[QUOTE="LouBoyd, post: 375223, member: 9253"] Perhaps I misunderstood Rocky's question . To determine what load and bullet gives what pressure in a wildcat cartridge the computer Program Quickload is quite helpful. To use it however you need to use bullets and powders which are in Quickload's database. The case capacity, neck diameter and case length are minimum information about the case and chamber. As a first approximation with the the powder type, case capacity, bullet type (including jacket material, mass, and length) bullet seating depth, and barrel length you can predict what velocity your load should have vs chamber pressure. Freebore is not part of Quickloads calculation, nor is primer energy. Combining the information from Quckloads calculation with actual bullet velocity measured by a chronograph will give a good estimate of the pressure curve in chamber of a wildcat cartridge. There are at least six parameters which define how a powder burns. Just guessing that the powder you're using is similar to a powder which is in the database can lead to very wrong estimates of the pressure curves even though the two powders might give the same velocity. There are also commercial strain gauge kits which can be fitted to most rifle actions to measure the chamber pressure curve directly. Accurate dimension of the chamber wall thickness needs to be knows as does the modulus of elasticity of the alloy the chamber is made of. When a rifle is fired the outside wall of the receiver expands linearly with internal pressure as long as the elastic limit of the receiver isn't exceeded, which it wont be for normal cartridge pressures. The strain gage measures how much the barrel stretches vs time when fired and a relative simple formula then calculates the pressure curve. From the pressure curve and the cartridge dimension the forces on the receiver and bolt can be determined. As to what the design maximum pressure for a given receiver might be that should be obtained from the receiver's designer and manufacturer. Hopefully the designer did thorough calculations and the manufacturer followed the design, particularly with the metallurgy and heat treating. [/QUOTE]
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Custom action pressure ceiling.
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