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Rifles, Reloading, Optics, Equipment
Reloading
Sinclair bump gauge error
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<blockquote data-quote="o2bmark" data-source="post: 3017121" data-attributes="member: 6358"><p>I found the issue with the sinclair comparator with my rifle (Christensen Arms CF barrel 308win) and my dies (Redding FL, Redding calibrated shell holder set) and have not tested other combinations of caliber and rifle.</p><p>The issue is interference from UNSIZED neck of fired case as they come from the rifle. By experimentation I found that the point of first contact with comparator was on the slope up from shoulder to neck which on the raw fired case was .346+" in diameter (wow, really loose/large chamber in neck!). My sized neck is .3360" in diameter. Nine thousandths play in neck is ridiculous (loaded round .337"), I prefer 2 to 3 thousandth in non-match bolt gun. If I only neck size a case to .336" leaving the body unsized then measurement with Sinclair system is consistent with all of my other methods of measurement. The error previously found was in the measurement of the fired case as it came from the rifle. Once the neck had been sized all measurements were consistent. When I resized several cases using a different Redding shellholder which stepped case insertion into die in .002" increments the Sinclair comparator showed .002" increases in headspace as it should. </p><p></p><p>Conclusions: The insert is too tight in diameter at the neck shoulder juncture for MY RIFLE. Given the overly large neck diameter of my rifle it may not be a problem for fired necks smaller than .3465". It certainly works with .336" necks. SAAMI gives .3442" for chamber neck diameter at the mouth and .3462" at the shoulder and my loading manuals show .344".</p><p>Additional lesson learned was that my precision aluminum turret press had more spring than I thought (requiring more cam over on shell holder than I like to insure full insertion into size die) and for now I'm going back to RCBS O press for FL resizing chores,</p><p>My rifle is a sub 1MOA gun reliably although I seldom shoot more than 300 yds with it. For open country and greater ranges I go for a bigger gun.</p><p></p><p>I apologize for not doing thorough testing before first posting but hopefully results may help someone eventually. So glad you guys are around.</p></blockquote><p></p>
[QUOTE="o2bmark, post: 3017121, member: 6358"] I found the issue with the sinclair comparator with my rifle (Christensen Arms CF barrel 308win) and my dies (Redding FL, Redding calibrated shell holder set) and have not tested other combinations of caliber and rifle. The issue is interference from UNSIZED neck of fired case as they come from the rifle. By experimentation I found that the point of first contact with comparator was on the slope up from shoulder to neck which on the raw fired case was .346+" in diameter (wow, really loose/large chamber in neck!). My sized neck is .3360" in diameter. Nine thousandths play in neck is ridiculous (loaded round .337"), I prefer 2 to 3 thousandth in non-match bolt gun. If I only neck size a case to .336" leaving the body unsized then measurement with Sinclair system is consistent with all of my other methods of measurement. The error previously found was in the measurement of the fired case as it came from the rifle. Once the neck had been sized all measurements were consistent. When I resized several cases using a different Redding shellholder which stepped case insertion into die in .002" increments the Sinclair comparator showed .002" increases in headspace as it should. Conclusions: The insert is too tight in diameter at the neck shoulder juncture for MY RIFLE. Given the overly large neck diameter of my rifle it may not be a problem for fired necks smaller than .3465". It certainly works with .336" necks. SAAMI gives .3442" for chamber neck diameter at the mouth and .3462" at the shoulder and my loading manuals show .344". Additional lesson learned was that my precision aluminum turret press had more spring than I thought (requiring more cam over on shell holder than I like to insure full insertion into size die) and for now I'm going back to RCBS O press for FL resizing chores, My rifle is a sub 1MOA gun reliably although I seldom shoot more than 300 yds with it. For open country and greater ranges I go for a bigger gun. I apologize for not doing thorough testing before first posting but hopefully results may help someone eventually. So glad you guys are around. [/QUOTE]
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Sinclair bump gauge error
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