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Rifles, Reloading, Optics, Equipment
Gunsmithing
Firing Pin Protrusion
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<blockquote data-quote="J E Custom" data-source="post: 1457001" data-attributes="member: 2736"><p>The pin protrusion is only one part of the equation. And this is why.</p><p></p><p>There so many factors that effect the firing pin performance with a firing pin that has the proper/recommended protrusion that it can pierce the primer or not even set it off .</p><p></p><p>The heavier the firing pin, the slower it is and requires a heavy spring</p><p>The impact travel may not be as much as the protrusion dimension.</p><p>the same is reversed with shorter lock times and lighter firing pins. They may not need as much protrusion to function properly.</p><p></p><p>One such instance was a super light firing pin that had .057 thousandths protrusion that had a history of misfires. Wanting to know why, I modified an Old tool for measuring protrusion by machining a point on it. After zeroing it on the bolt face, I then moved to the pin strike indentation. The "Actual" depth of the strike was less than .040 thousandths. we then changed back to a standard weight firing pin and the strike depth was back to almost the same as the measured protrusion. (.054) </p><p></p><p>This phenomenon is not unusual for heavy firing pins ether, the heavy firing pin is slowed by the primer and may not penetrate as deep as it is set. so If you are having problems, measure the actual firing pin impact and this should tell you where the problem is. You may need to change firing pin spring, the firing pin it's self or make sure that the firing pin assembly if free to move it the bolt. (This is a common occurrence in ARs that foul the firing pin, and bolt actions where the spring snakes down the firing pin and rubs on the inside of the bolt.(Slowing the firing pin reducing the strike energy).</p><p></p><p>The recommended protrusion is a good start and for the most part sufficient, but sometimes, some trouble shooting is required. Measuring the actual strike depth will tell you if you have a problem or not. Sometimes this measuring process is necessary if you change primers because of cup thickness and hardness. </p><p></p><p>I am not sure if there is a desired depth for the pin strike but it does have an effect on the consistency of the ignition of the primer depending on the construction of the primer and the compound used.</p><p>(If anyone knows what this is please educate me).</p><p></p><p>J E CUSTOM</p></blockquote><p></p>
[QUOTE="J E Custom, post: 1457001, member: 2736"] The pin protrusion is only one part of the equation. And this is why. There so many factors that effect the firing pin performance with a firing pin that has the proper/recommended protrusion that it can pierce the primer or not even set it off . The heavier the firing pin, the slower it is and requires a heavy spring The impact travel may not be as much as the protrusion dimension. the same is reversed with shorter lock times and lighter firing pins. They may not need as much protrusion to function properly. One such instance was a super light firing pin that had .057 thousandths protrusion that had a history of misfires. Wanting to know why, I modified an Old tool for measuring protrusion by machining a point on it. After zeroing it on the bolt face, I then moved to the pin strike indentation. The "Actual" depth of the strike was less than .040 thousandths. we then changed back to a standard weight firing pin and the strike depth was back to almost the same as the measured protrusion. (.054) This phenomenon is not unusual for heavy firing pins ether, the heavy firing pin is slowed by the primer and may not penetrate as deep as it is set. so If you are having problems, measure the actual firing pin impact and this should tell you where the problem is. You may need to change firing pin spring, the firing pin it's self or make sure that the firing pin assembly if free to move it the bolt. (This is a common occurrence in ARs that foul the firing pin, and bolt actions where the spring snakes down the firing pin and rubs on the inside of the bolt.(Slowing the firing pin reducing the strike energy). The recommended protrusion is a good start and for the most part sufficient, but sometimes, some trouble shooting is required. Measuring the actual strike depth will tell you if you have a problem or not. Sometimes this measuring process is necessary if you change primers because of cup thickness and hardness. I am not sure if there is a desired depth for the pin strike but it does have an effect on the consistency of the ignition of the primer depending on the construction of the primer and the compound used. (If anyone knows what this is please educate me). J E CUSTOM [/QUOTE]
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