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Rifles, Reloading, Optics, Equipment
Reloading
Shoulder bump FL sizing and measurements
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<blockquote data-quote="Tac-O" data-source="post: 1851817" data-attributes="member: 109994"><p>I want to update this thread as I made a discovery recently and think this information would be helpful to others. I was attempting to use my FL sizing die to bump the shoulders back 0.002". I found that my fired cases would max out at about 1.742 for base to datum (I think... I can't remember exactly off the top of my head). Chambering a case of this size starts giving resistance through the full length of closing the bolt, so this is the length of my chamber for fired cases. No matter how I set up my FL sizing die, it would cause my base to datum measurement on the case to increase! If it was a 1x fired case and was only 1.740, after sizing it would be 1.742. If it was a 2x fired case and measured 1.742, then after sizing it would measure 1.743! I could set my die up to the manufacturer's instructions for a SAAMI spec FL resize and I'd still end up with bolt resistance when closing the bolt after a 2 or 3 firings.</p><p></p><p>I happen to find this article the other day:</p><p></p><p><a href="http://bulletin.accurateshooter.com/2010/09/bedeviled-by-bump-when-full-length-dies-dont-work/" target="_blank">http://bulletin.accurateshooter.com/2010/09/bedeviled-by-bump-when-full-length-dies-dont-work/</a></p><p></p><p>After reading that article, I determined that my die was just a little bit too long on the inside. So here's what I did:</p><p></p><p>- put a sheet of 400 grit sand paper on a very flat surface (stainless top table)</p><p>- put some cutting oil on the sand paper</p><p>- sanded down the bottom of my FL sizing die by 0.004-0.005".</p><p></p><p>Now when setting up my die, I can set it up to have just a slight bit of cam over and it will bump my shoulders back from 1.742 to 1.740.</p><p></p><p>From what I've found reading, there's other ways of accomplishing this; grinding down top of shellholder, etc. Each have their own merits and drawbacks. In my case, if I get a different rifle of same chambering or have a new barrel put in, then my customized die might not work anymore. Or maybe it will. No need to worry about that since Lee dies are affordable and now I can actually size my cases the way I want!</p></blockquote><p></p>
[QUOTE="Tac-O, post: 1851817, member: 109994"] I want to update this thread as I made a discovery recently and think this information would be helpful to others. I was attempting to use my FL sizing die to bump the shoulders back 0.002". I found that my fired cases would max out at about 1.742 for base to datum (I think... I can't remember exactly off the top of my head). Chambering a case of this size starts giving resistance through the full length of closing the bolt, so this is the length of my chamber for fired cases. No matter how I set up my FL sizing die, it would cause my base to datum measurement on the case to increase! If it was a 1x fired case and was only 1.740, after sizing it would be 1.742. If it was a 2x fired case and measured 1.742, then after sizing it would measure 1.743! I could set my die up to the manufacturer's instructions for a SAAMI spec FL resize and I'd still end up with bolt resistance when closing the bolt after a 2 or 3 firings. I happen to find this article the other day: [URL]http://bulletin.accurateshooter.com/2010/09/bedeviled-by-bump-when-full-length-dies-dont-work/[/URL] After reading that article, I determined that my die was just a little bit too long on the inside. So here's what I did: - put a sheet of 400 grit sand paper on a very flat surface (stainless top table) - put some cutting oil on the sand paper - sanded down the bottom of my FL sizing die by 0.004-0.005". Now when setting up my die, I can set it up to have just a slight bit of cam over and it will bump my shoulders back from 1.742 to 1.740. From what I've found reading, there's other ways of accomplishing this; grinding down top of shellholder, etc. Each have their own merits and drawbacks. In my case, if I get a different rifle of same chambering or have a new barrel put in, then my customized die might not work anymore. Or maybe it will. No need to worry about that since Lee dies are affordable and now I can actually size my cases the way I want! [/QUOTE]
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Shoulder bump FL sizing and measurements
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