{"id":635,"date":"2023-10-06T23:05:24","date_gmt":"2023-10-06T23:05:24","guid":{"rendered":"https:\/\/tactical-dailynews.com\/?p=635"},"modified":"2023-10-06T23:05:25","modified_gmt":"2023-10-06T23:05:25","slug":"using-chamber-concentricity-to-fit-ammo-to-your-rifle","status":"publish","type":"post","link":"https:\/\/tactical-dailynews.com\/?p=635","title":{"rendered":"Using Chamber Concentricity To Fit Ammo To Your Rifle"},"content":{"rendered":"<div>\n<h2 class=\"wp-block-heading\" id=\"h-leave-that-shoulder-alone-here-s-how-to-fit-ammo-to-your-rifle-using-chamber-concentricity\"><strong>Leave that shoulder alone! Here\u2019s how to fit ammo to your rifle using chamber concentricity.<\/strong><\/h2>\n<p>Bottlenecked cartridges have many different means of headspacing, from using a rim\u2014so popular among the lever-action cartridges\u2014to the Holland &amp; Holland belted design, to the true rimless cartridges that use the shoulder for headspacing. And while the goal for creating ammunition is to have the cartridge slip easily into the chamber, sometimes that formula doesn\u2019t give the best possible accuracy.<\/p>\n<p>If you reload your ammunition, you can control some of the dimensions, and you can give yourself an advantage in the accuracy department.<\/p>\n<figure class=\"wp-block-image size-full\"><noscript><\/noscript><img decoding=\"async\" fetchpriority=\"high\" width=\"800\" height=\"500\" src=\"https:\/\/gundigest.com\/wp-content\/uploads\/chamber-concentricity.jpg\" alt=\"chamber-concentricity\" class=\"lazyload wp-image-290937\" srcset=\"https:\/\/gundigest.com\/wp-content\/uploads\/chamber-concentricity.jpg 800w, https:\/\/gundigest.com\/wp-content\/uploads\/chamber-concentricity-300x188.jpg 300w, https:\/\/gundigest.com\/wp-content\/uploads\/chamber-concentricity-768x480.jpg 768w, https:\/\/gundigest.com\/wp-content\/uploads\/chamber-concentricity-696x435.jpg 696w, https:\/\/gundigest.com\/wp-content\/uploads\/chamber-concentricity-672x420.jpg 672w\" data-sizes=\"(max-width: 800px) 100vw, 800px\"\/><figcaption class=\"wp-element-caption\">Proper chamber concentricity will enhance accuracy and put a smile on a shooter\u2019s face. <em>Photo: Massaro Media Group.<\/em><\/figcaption><\/figure>\n<h3 class=\"wp-block-heading\" id=\"h-managing-variables-and-expectations\"><strong>Managing Variables And Expectations<\/strong><\/h3>\n<p>First, to understand things properly, we must realize that not all chambers are cut in the same manner. Yes, our factory guns and even custom jobs do the best to keep things as uniform as possible, but even with the modern level of CNC machining, precision go\/no-go gauges and computer designs, our chambers might not be cut in a uniform manner from gun to gun. Couple that idea with the fact that our mass-produced ammunition\u2014while I feel it is the best that is has ever been\u2014will have slight variations from brand to brand \u2026 and even from lot to lot.<\/p>\n<p>Now, the differences in accuracy might not mean a whole helluva lot to the deer hunter who reaches for the rifle once a year. He or she will often sight the rifle before the season, taking a few shots to make sure they can effectively hit a paper plate (roughly the size of a deer\u2019s vital organs) or a bit better\u2014and that\u2019s fine, if that\u2019s your hunting style. But for someone preparing for a hunt at longer ranges, or someone who is serious about target shooting or the various rifle competitions, a different mindset and level of precision is needed.<\/p>\n<h3 class=\"wp-block-heading\" id=\"h-piece-by-piece\"><strong>Piece By Piece<\/strong><\/h3>\n<p>Looking at the first and most basic premise of reloading a metallic cartridge, the resizing die is used to reduce the case from its fired dimension back to the SAAMI-specified dimensions. The fired cartridge has expanded to the dimensions of the chamber as a result of the pressures generated from the firing sequence. It\u2019s the difference between the original SAAMI dimensions and fired (chamber) dimensions that allow the cartridge to easily insert into the chamber, but it\u2019s also that difference in dimension that reduces chamber concentricity.<\/p>\n<p>When you measure the amount of expansion on some of the belted cases\u2014famous for stretching just above the belt\u2014you might see as much as 0.020-inch lengthening on the first firing. It\u2019s no small wonder that we see case head separation among the belted cases, especially if we are bringing things back to the SAAMI dimension after each firing. That level of stress is too much for even the finest brass cases.<\/p>\n<figure class=\"wp-block-image size-full\"><noscript><img loading=\"lazy\" decoding=\"async\" width=\"800\" height=\"500\" src=\"https:\/\/gundigest.com\/wp-content\/uploads\/chamber-concentricity-belted.jpg\" alt=\"chamber-concentricity-belted\" class=\"wp-image-290939\" srcset=\"https:\/\/gundigest.com\/wp-content\/uploads\/chamber-concentricity-belted.jpg 800w, https:\/\/gundigest.com\/wp-content\/uploads\/chamber-concentricity-belted-300x188.jpg 300w, https:\/\/gundigest.com\/wp-content\/uploads\/chamber-concentricity-belted-768x480.jpg 768w, https:\/\/gundigest.com\/wp-content\/uploads\/chamber-concentricity-belted-696x435.jpg 696w, https:\/\/gundigest.com\/wp-content\/uploads\/chamber-concentricity-belted-672x420.jpg 672w\" sizes=\"auto, (max-width: 800px) 100vw, 800px\"\/><\/noscript><img loading=\"lazy\" decoding=\"async\" width=\"800\" height=\"500\" src=\"https:\/\/gundigest.com\/wp-content\/uploads\/chamber-concentricity-belted.jpg\" alt=\"chamber-concentricity-belted\" class=\"lazyload wp-image-290939\" srcset=\"https:\/\/gundigest.com\/wp-content\/uploads\/chamber-concentricity-belted.jpg 800w, https:\/\/gundigest.com\/wp-content\/uploads\/chamber-concentricity-belted-300x188.jpg 300w, https:\/\/gundigest.com\/wp-content\/uploads\/chamber-concentricity-belted-768x480.jpg 768w, https:\/\/gundigest.com\/wp-content\/uploads\/chamber-concentricity-belted-696x435.jpg 696w, https:\/\/gundigest.com\/wp-content\/uploads\/chamber-concentricity-belted-672x420.jpg 672w\" data-sizes=\"(max-width: 800px) 100vw, 800px\"\/><figcaption class=\"wp-element-caption\">Belted cases headspace off the belt and will stretch to the point that the case will separate. Leaving the shoulder in same position as the case has when fired will drastically reduce this phenomenon. <em>Photo: Massaro Media Group.<\/em><\/figcaption><\/figure>\n<p>If we\u2019re talking about a rimless case, where the shoulder handles the headspacing, it isn\u2019t difficult to see why accuracy could suffer if the ammo and chamber aren\u2019t quite matching up very well.<\/p>\n<h3 class=\"wp-block-heading\" id=\"h-the-neck-sizing-technique\"><strong>The Neck-Sizing Technique<\/strong><\/h3>\n<p>Reloaders have long taken steps to keep cases as close to chamber conformation as possible. Early on, it was the neck sizing technique that was the most popular means. When a cartridge is \u201cneck sized,\u201d only the neck is reduced back to original dimension in order to provide enough tension to hold the projectile; the shoulder position and body diameter of the fired case are left \u201cas is.\u201d<\/p>\n<p>This technique certainly works, though it does have a couple of pitfalls. Generally speaking, the neck-sized ammunition is only suitable for bolt-action rifles, which have the power to close the bolt on the ammunition of larger dimension. Lever guns and auto-loaders can quickly show the shooter the rifle isn\u2019t happy at all with this type of ammunition.<\/p>\n<figure class=\"wp-block-image size-full\"><noscript><img loading=\"lazy\" decoding=\"async\" width=\"800\" height=\"500\" src=\"https:\/\/gundigest.com\/wp-content\/uploads\/chamber-concentricity-neck-sizing.jpg\" alt=\"chamber-concentricity-neck-sizing\" class=\"wp-image-290940\" srcset=\"https:\/\/gundigest.com\/wp-content\/uploads\/chamber-concentricity-neck-sizing.jpg 800w, https:\/\/gundigest.com\/wp-content\/uploads\/chamber-concentricity-neck-sizing-300x188.jpg 300w, https:\/\/gundigest.com\/wp-content\/uploads\/chamber-concentricity-neck-sizing-768x480.jpg 768w, https:\/\/gundigest.com\/wp-content\/uploads\/chamber-concentricity-neck-sizing-696x435.jpg 696w, https:\/\/gundigest.com\/wp-content\/uploads\/chamber-concentricity-neck-sizing-672x420.jpg 672w\" sizes=\"auto, (max-width: 800px) 100vw, 800px\"\/><\/noscript><img loading=\"lazy\" decoding=\"async\" width=\"800\" height=\"500\" src=\"https:\/\/gundigest.com\/wp-content\/uploads\/chamber-concentricity-neck-sizing.jpg\" alt=\"chamber-concentricity-neck-sizing\" class=\"lazyload wp-image-290940\" srcset=\"https:\/\/gundigest.com\/wp-content\/uploads\/chamber-concentricity-neck-sizing.jpg 800w, https:\/\/gundigest.com\/wp-content\/uploads\/chamber-concentricity-neck-sizing-300x188.jpg 300w, https:\/\/gundigest.com\/wp-content\/uploads\/chamber-concentricity-neck-sizing-768x480.jpg 768w, https:\/\/gundigest.com\/wp-content\/uploads\/chamber-concentricity-neck-sizing-696x435.jpg 696w, https:\/\/gundigest.com\/wp-content\/uploads\/chamber-concentricity-neck-sizing-672x420.jpg 672w\" data-sizes=\"(max-width: 800px) 100vw, 800px\"\/><figcaption class=\"wp-element-caption\">RCBS neck-sizing bushing dies are a solid means of neck sizing cases without overstretching the brass. <em>Photo: Massaro Media Group.<\/em><\/figcaption><\/figure>\n<p>Also, the neck-sized brass will usually be reserved for the rifle from which it was fired; the slight variations in chamber dimensions can prevent neck-sized cases from one rifle being used in another, as the bolt might not close at all. Plus, even when done properly in a bolt-action rifle, feeding can be much less smooth than regular ammunition.<\/p>\n<p>For the target shooter, this might not be a huge deal, but for the hunter it could make big difference, especially when in pursuit of dangerous game, where a follow-up shot is imperative. Caveats aside, most manufacturers of reloading dies still offer a neck sizing die as an option. If you want to take the neck-sizing route, I recommend opting for a bushing die to minimize the amount of neck stretch during resizing.<\/p>\n<h3 class=\"wp-block-heading\" id=\"h-shoulder-work\"><strong>Shoulder Work<\/strong><\/h3>\n<p>The other means of obtaining the best chamber concentricity, yet still offering smooth and rapid feeding, is to measure the amount of shoulder movement from SAAMI spec to your fired cases. Redding\u2019s Instant Indicator and Bullet Comparator is what you want to measure exactly how much your cases are stretching upon firing.<\/p>\n<p>Using a SAAMI-spec dummy case as a reference point, the Comparator will quickly show you how much your fired cases vary from the specified dimensions. When used in conjunction with the Redding Competition Shellholder Set, it\u2019ll allow the reloader to use a resizing die to shrink all the exterior dimensions of the fired case \u2026 without moving the shoulder.<\/p>\n<p>It works like this: After using the dial indicator to observe the difference in your fired cases and the SAAMI-spec dimension, you\u2019ll arrive at an average dimensional variance. So, for example, if you were to compare a half-dozen of your fired cases to the SAAMI-spec dummy, seeing a difference of 0.006 inch, you could grab the correlative shellholder and resize your cases. Redding\u2019s Competition set of shellholders offer five different depths\u2014ranging from 0.002 to 0.010 inch\u2014for each family of cases. At worst, you might have to use a shoulder dimension 0.01 inch different from the observed variation, but that\u2019ll still enhance accuracy.<\/p>\n<p>What this does is resize your case\u2014body diameter, neck dimension, etc.\u2014while leaving the shoulder where it was after being fired. Cartridges loaded in this manner will give the benefits of a fully resized case in the feeding department but will best match your rifle\u2019s chamber by keeping the shoulder up against the chamber wall. Yes, these cartridges will also be rifle-specific, in that they are best reserved for the rifle in which they were initially fired, but the chamber concentricity will invariably improve, and with that\u2014at least in my experience\u2014the accuracy, velocity spread and uniformity will also improve.<\/p>\n<p>I\u2019ve used these shellholders to cut the groups size of a .308 Winchester in nearly half, and drastically reduce the velocity spread as well. They surely have extended the life of my .300 Winchester Magnum and .300 H&amp;H Magnum brass. In fact, when I run into a problem rifle, I reach for the silly little shellholder trick if the gun seems to be a bit finicky, and there have been several instances where a seemingly lame load has come to shine once the shoulder has been properly mated to the chamber.<\/p>\n<p>Bottom line: The Comparator will run about $180 street price, and a set of the Competition Shellholders cost another $80 or so. With the two, you can easily customize your ammunition to best match the dimensions of your rifle\u2019s chamber, resulting in an easy-to-feed cartridge that gives the best concentricity available. I feel rather confident saying that you\u2019ll see an improvement in both accuracy and consistent velocity; this is, after all, what we reloaders seek most.\u00a0<\/p>\n<p><em><strong>Editor&#8217;s Note:<\/strong>\u00a0This article originally appeared in the October 2023 issue of\u00a0<a href=\"https:\/\/gundigestservice.com\/customer\/subscribe.php\" target=\"_blank\" rel=\"noreferrer noopener\">Gun Digest the Magazine<\/a><\/em>.<\/p>\n<hr\/>\n<p><strong>More On Reloading:<\/strong><\/p>\n<div class=\"code-block code-block-27\" style=\"margin: 8px 0; clear: both;\">\n<div style=\"border: 2px solid #e5e5e5; padding: 20px; border-radius: 10px; font-family: Arial, sans-serif;\"><noscript><img loading=\"lazy\" decoding=\"async\" class=\"alignright size-medium wp-image-271572\" src=\"https:\/\/gundigest.com\/wp-content\/uploads\/44-Targetposters-pack-GD-reduced-300-300x235.jpg\" alt=\"44-Targetposters-pack-GD-reduced-300\" width=\"300\" height=\"235\"\/><\/noscript><img loading=\"lazy\" decoding=\"async\" class=\"lazyload alignright size-medium wp-image-271572\" src=\"https:\/\/gundigest.com\/wp-content\/uploads\/44-Targetposters-pack-GD-reduced-300-300x235.jpg\" alt=\"44-Targetposters-pack-GD-reduced-300\" width=\"300\" height=\"235\"\/><\/p>\n<h2 style=\"color: #FF4500; text-align: center;\">\ud83c\udfaf Next Step: Get Your FREE Printable Target Pack!<\/h2>\n<p>Dive into precision shooting with our <strong>62 Exclusive MOA Targets<\/strong> featuring DOT Drills. Perfect for both rifle and handgun enthusiasts, these targets are designed for accuracy, especially for long-range shots.<\/p>\n<h3>Why You&#8217;ll Love This Pack:<\/h3>\n<ul>\n<li>\ud83c\udfaf <strong>Expertly Crafted:<\/strong> Brought to you in partnership with the renowned Storm Tactical.<\/li>\n<li>\ud83c\udfaf <strong>Versatile Use:<\/strong> Suitable for both rifle and handgun range sessions.<\/li>\n<li>\ud83c\udfaf <strong>Precision Design:<\/strong> Target grids and bullseyes meticulously measured in MOA for the best shooting experience.<\/li>\n<\/ul>\n<p><strong>Bonus:<\/strong> By grabbing this offer, you&#8217;ll also be subscribing to the Gun Digest email newsletter, keeping you updated with the latest in the world of firearms.<\/p>\n<h3 style=\"color: #FF4500; text-align: center;\">Don&#8217;t miss out!<\/h3>\n<p>Simply enter your email below, and we&#8217;ll send your downloadable target pack straight to your inbox.<\/p>\n<\/p><\/div>\n<\/div>\n<p> <!-- AI CONTENT END 1 --><\/div>\n","protected":false},"excerpt":{"rendered":"<p>Leave that shoulder alone! Here\u2019s how to fit ammo to your rifle using chamber concentricity. Bottlenecked cartridges have many different means of headspacing, from using a rim\u2014so popular among the lever-action cartridges\u2014to the Holland &amp; Holland belted design, to the true rimless cartridges that use the shoulder for headspacing. And while the goal for creating [&hellip;]<\/p>\n","protected":false},"author":1,"featured_media":636,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[5],"tags":[],"class_list":["post-635","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-tactical-gear"],"_links":{"self":[{"href":"https:\/\/tactical-dailynews.com\/index.php?rest_route=\/wp\/v2\/posts\/635","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/tactical-dailynews.com\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/tactical-dailynews.com\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/tactical-dailynews.com\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/tactical-dailynews.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=635"}],"version-history":[{"count":1,"href":"https:\/\/tactical-dailynews.com\/index.php?rest_route=\/wp\/v2\/posts\/635\/revisions"}],"predecessor-version":[{"id":637,"href":"https:\/\/tactical-dailynews.com\/index.php?rest_route=\/wp\/v2\/posts\/635\/revisions\/637"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/tactical-dailynews.com\/index.php?rest_route=\/wp\/v2\/media\/636"}],"wp:attachment":[{"href":"https:\/\/tactical-dailynews.com\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=635"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/tactical-dailynews.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=635"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/tactical-dailynews.com\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=635"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}