{"id":2990,"date":"2020-10-06T08:33:37","date_gmt":"2020-10-06T08:33:37","guid":{"rendered":"https:\/\/www.ammoman.com\/blog\/?p=2990"},"modified":"2021-03-09T13:37:21","modified_gmt":"2021-03-09T13:37:21","slug":"measuring-groups-with-extreme-spread-vs-mean-radius","status":"publish","type":"post","link":"https:\/\/www.ammoman.com\/blog\/measuring-groups-with-extreme-spread-vs-mean-radius\/","title":{"rendered":"Measuring Groups with Extreme Spread Vs. Mean Radius"},"content":{"rendered":"<h1><span style=\"font-weight: 400;\">What Is Mean Radius, And How Do You Use It?<\/span><\/h1>\n<p><span style=\"font-weight: 400;\">We talk about shot groups all the time. We brag about a \u00bd inch group at 100 yards with our most beloved precision rifle, but what are we actually talking about when we talk about shot grouping? Are shot groups the best way to measure accuracy, or is there something that is more statistically valid we can use?\u00a0<\/span><\/p>\n<p><span style=\"font-weight: 400;\">When we measure the shot grouping on our target, we typically measure extreme spread. This is usually the distance between the centers of the two most distant holes in the group of shots on the target. At first glance, this seems like a good way to measure accuracy. I mean, we shoot the target, we measure the results. Seems simple, right?\u00a0<\/span><\/p>\n<h3><span style=\"font-weight: 400;\">Extreme Spread vs Mean Radius<\/span><\/h3>\n<p><span style=\"font-weight: 400;\">However, the problem with this technique is what we are really measuring is the distance between the two worst shots of a group. We\u2019re judging our performance by how bad we are at one moment, not our consistent performance. However, we can gain some idea of how we perform consistently by shooting a number of groups and then averaging them together. The problem is, we have to shoot a fair amount of ammo to get a good representation of our actual accuracy results.\u00a0<\/span><\/p>\n<p><span style=\"font-weight: 400;\">For instance, in the past, when we test a gun here at Ammoman, we shoot four groups of five rounds each and then average them together. Sounds good, right? That\u2019s 20 shots, it should tell us how accurate the gun is, right? The problem is that in reality, we are only measuring eight shots: The worst two shots out of each of those five round groups. We need a way of measuring shot grouping that measures every shot we take, not just the worst two of each group we shot.\u00a0<\/span><\/p>\n<h3><span style=\"font-weight: 400;\">Let\u2019s Get Mean (Radius)<\/span><\/h3>\n<p><span style=\"font-weight: 400;\"><a href=\"https:\/\/www.ammoman.com\/blog\/media\/group_measurements.jpg\" data-rel=\"lightbox-image-0\" data-magnific_type=\"image\" data-rl_title=\"\" data-rl_caption=\"\"><img loading=\"lazy\" decoding=\"async\" class=\"alignright wp-image-3005\" title=\"\" src=\"https:\/\/www.ammoman.com\/blog\/media\/group_measurements-100x300.jpg\" alt=\"measuring shot groups\" width=\"150\" height=\"450\" srcset=\"https:\/\/www.ammoman.com\/blog\/media\/group_measurements-100x300.jpg 100w, https:\/\/www.ammoman.com\/blog\/media\/group_measurements-341x1024.jpg 341w, https:\/\/www.ammoman.com\/blog\/media\/group_measurements-512x1536.jpg 512w, https:\/\/www.ammoman.com\/blog\/media\/group_measurements-333x1000.jpg 333w, https:\/\/www.ammoman.com\/blog\/media\/group_measurements.jpg 533w\" sizes=\"auto, (max-width: 150px) 100vw, 150px\" \/><\/a>Enter mean radius. This gets complicated to determine, because you need to find the mathematical center of the group you shot. Then you measure the distance of each individual shot from the mathematical center and average those distances together. With mean radius, we are still averaging shots together. The difference is, we are measuring the distance from each shot to every other shot, not just the two worst shots from each group. When we use mean radius to measure our shot grouping, all the shots matter in the group, not just the two worst ones.\u00a0<\/span><\/p>\n<p><span style=\"font-weight: 400;\">But why bother, you say? For one thing, the U.S. Military has been using <\/span><a href=\"https:\/\/apps.dtic.mil\/dtic\/tr\/fulltext\/u2\/1034885.pdf\"><span style=\"font-weight: 400;\">mean radius to evaluate the performance<\/span><\/a><span style=\"font-weight: 400;\"> of their rifles for quite some time now, going back at least as far as the early 20th century and the trials for the M1903 Springfield rifle.\u00a0<\/span><\/p>\n<p><span style=\"font-weight: 400;\">So I guess it works.\u00a0<\/span><\/p>\n<h3><span style=\"font-weight: 400;\">Mean Radius Means Lots Of Math<\/span><\/h3>\n<p><span style=\"font-weight: 400;\">However, measuring mean radius requires a lot of mathematical heavy lifting. Fortunately for all of us, today\u2019s computers can do that lifting for us. That is why we are rolling out the <a href=\"https:\/\/www.ammoman.com\/blog\/sga\/\">Ammoman Shot Group Analyzer<\/a>. This handy online tool will allow you to upload a photo of your target, set the target size, measure both the extreme spread of your group and the mean radius, and then save your results for later analysis.\u00a0<\/span><\/p>\n<p><span style=\"font-weight: 400;\"><a href=\"https:\/\/www.ammoman.com\/blog\/media\/shot_group_analysis_target.jpg\" data-rel=\"lightbox-image-1\" data-magnific_type=\"image\" data-rl_title=\"\" data-rl_caption=\"\"><img loading=\"lazy\" decoding=\"async\" class=\"alignright wp-image-3003\" title=\"\" src=\"https:\/\/www.ammoman.com\/blog\/media\/shot_group_analysis_target-276x300.jpg\" alt=\"Shots on target\" width=\"253\" height=\"275\" srcset=\"https:\/\/www.ammoman.com\/blog\/media\/shot_group_analysis_target-276x300.jpg 276w, https:\/\/www.ammoman.com\/blog\/media\/shot_group_analysis_target-941x1024.jpg 941w, https:\/\/www.ammoman.com\/blog\/media\/shot_group_analysis_target-768x836.jpg 768w, https:\/\/www.ammoman.com\/blog\/media\/shot_group_analysis_target-1412x1536.jpg 1412w, https:\/\/www.ammoman.com\/blog\/media\/shot_group_analysis_target-610x664.jpg 610w, https:\/\/www.ammoman.com\/blog\/media\/shot_group_analysis_target-1080x1175.jpg 1080w, https:\/\/www.ammoman.com\/blog\/media\/shot_group_analysis_target-627x682.jpg 627w, https:\/\/www.ammoman.com\/blog\/media\/shot_group_analysis_target.jpg 1600w\" sizes=\"auto, (max-width: 253px) 100vw, 253px\" \/><\/a>For example, let\u2019s look at a series of groups from a recent <\/span><a href=\"https:\/\/www.ammoman.com\/blog\/1911-vs-glock\/\"><span style=\"font-weight: 400;\">1911 versus Glock test<\/span><\/a><span style=\"font-weight: 400;\">. These four groups of Fiocchi 115 grain 9mm FMJ were shot at a distance of 15 yards using a stock Glock 19. Let\u2019s compare the results of measuring extreme spread versus mean radius.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">At first glance, the group on the left-hand side of the target appears significantly smaller than the other three groups. What that group size is measuring, however, is the distance between the two worst shots in that string of fire. Once we start to look at the mean radius of each group, a different story appears. <\/span><\/p>\n<p><a href=\"https:\/\/www.ammoman.com\/blog\/media\/target_array.jpg\" data-rel=\"lightbox-image-2\" data-magnific_type=\"image\" data-rl_title=\"\" data-rl_caption=\"\"><img loading=\"lazy\" decoding=\"async\" class=\"aligncenter wp-image-2992 size-full\" title=\"\" src=\"https:\/\/www.ammoman.com\/blog\/media\/target_array.jpg\" alt=\"comparing extreme spread vs mean radius\" width=\"1600\" height=\"407\" srcset=\"https:\/\/www.ammoman.com\/blog\/media\/target_array.jpg 1600w, https:\/\/www.ammoman.com\/blog\/media\/target_array-300x76.jpg 300w, https:\/\/www.ammoman.com\/blog\/media\/target_array-1024x260.jpg 1024w, https:\/\/www.ammoman.com\/blog\/media\/target_array-768x195.jpg 768w, https:\/\/www.ammoman.com\/blog\/media\/target_array-1536x391.jpg 1536w, https:\/\/www.ammoman.com\/blog\/media\/target_array-610x155.jpg 610w, https:\/\/www.ammoman.com\/blog\/media\/target_array-1080x275.jpg 1080w, https:\/\/www.ammoman.com\/blog\/media\/target_array-627x159.jpg 627w\" sizes=\"auto, (max-width: 1600px) 100vw, 1600px\" \/><\/a><\/p>\n\n<table id=\"tablepress-20\" class=\"tablepress tablepress-id-20\">\n<tbody>\n<tr class=\"row-1\">\n\t<td class=\"column-1\">Shot Group 1<br \/>\nExtreme Spread<br \/>\n2.05 in<br \/>\nMean Radius<br \/>\n1.99 in<\/td><td class=\"column-2\">Shot Group 2<br \/>\nExtreme Spread<br \/>\n3.5 in<br \/>\nMean Radius<br \/>\n3.15 in<\/td><td class=\"column-3\">Shot Group 3<br \/>\nExtreme Spread<br \/>\n3.19 in<br \/>\nMean Radius<br \/>\n2.27 in<\/td><td class=\"column-4\">Shot Group 4<br \/>\nExtreme Spread<br \/>\n2.75 in<br \/>\nMean Radius<br \/>\n2.01 in<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<!-- #tablepress-20 from cache -->\n<p><span style=\"font-weight: 400;\">Using extreme spread to measure groups does work, but it requires more effort (and more ammo) to achieve statistically significant results.\u00a0<\/span><\/p>\n<h3><span style=\"font-weight: 400;\">Save Range Time, Save Ammo<\/span><\/h3>\n<p><span style=\"font-weight: 400;\">With extreme spread, you get one data point for every group you shoot. However, by using mean radius to measure groups, you now have one data point for every shot you take. This greatly speeds up the process of gathering data on the performance of your gun and ammunition. Using the <a href=\"https:\/\/www.ammoman.com\/blog\/sga\/\">Ammoman Shot Group Analyzer<\/a>, you no longer need to shoot four or more five shot groups to get an idea of the capabilities of your gear. Because the Shot Group Analyzer uses mean radius to measure the distance between each shot on the target, you can get statistically significant information with much less ammo.\u00a0<\/span><\/p>\n<p><span style=\"font-weight: 400;\">Extreme spread gives you an idea of what your worst-case performance might look like. It\u2019s also easier to measure, and so that\u2019s what we use. However, now that it\u2019s fast and easy to measure your groups with the Ammoman Shot Group Analyzer, you can quickly assess the down-range performance of your gear with a minimal use of your precious ammo supply,\u00a0leaving you with better feedback about your shooting so you can maximize your potential with each trip to the range.<\/span><\/p>\n<p>&nbsp;<\/p>\n","protected":false},"excerpt":{"rendered":"<p>What Is Mean Radius, And How Do You Use It? We talk about shot groups all the time. We brag about a \u00bd inch group at 100 yards with our most beloved precision rifle, but what are we actually talking about when we talk about shot grouping? Are shot groups the best way to measure [&hellip;]<\/p>\n","protected":false},"author":3,"featured_media":2999,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_et_pb_use_builder":"","_et_pb_old_content":"","_et_gb_content_width":"","footnotes":""},"categories":[18,5,12,13,11,19,10],"tags":[],"class_list":["post-2990","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-competition","category-guns-201","category-outdoor-range","category-pistol-shooting-tips","category-practice","category-rifle-shooting-tips","category-training","et-has-post-format-content","et_post_format-et-post-format-standard"],"yoast_head":"<!-- This site is optimized with the Yoast SEO plugin v25.9 - https:\/\/yoast.com\/wordpress\/plugins\/seo\/ -->\n<title>Measuring Groups with Extreme Spread Vs. Mean Radius - AmmoMan School of Guns Blog<\/title>\n<meta name=\"description\" content=\"We use extreme spread to measure groups because it&#039;s quick and easy to calculate. However, that&#039;s not how the military does it: They use mean radius. Let&#039;s see why.\" \/>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/www.ammoman.com\/blog\/measuring-groups-with-extreme-spread-vs-mean-radius\/\" \/>\n<meta property=\"og:locale\" content=\"en_US\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"Measuring Groups with Extreme Spread Vs. Mean Radius - AmmoMan School of Guns Blog\" \/>\n<meta property=\"og:description\" content=\"We use extreme spread to measure groups because it&#039;s quick and easy to calculate. However, that&#039;s not how the military does it: They use mean radius. 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Mean Radius"}]},{"@type":"WebSite","@id":"https:\/\/www.ammoman.com\/blog\/#website","url":"https:\/\/www.ammoman.com\/blog\/","name":"AmmoMan School of Guns Blog","description":"A blog about firearms, ammo and more","publisher":{"@id":"https:\/\/www.ammoman.com\/blog\/#organization"},"potentialAction":[{"@type":"SearchAction","target":{"@type":"EntryPoint","urlTemplate":"https:\/\/www.ammoman.com\/blog\/?s={search_term_string}"},"query-input":{"@type":"PropertyValueSpecification","valueRequired":true,"valueName":"search_term_string"}}],"inLanguage":"en-US"},{"@type":"Organization","@id":"https:\/\/www.ammoman.com\/blog\/#organization","name":"AmmoMan.com","url":"https:\/\/www.ammoman.com\/blog\/","logo":{"@type":"ImageObject","inLanguage":"en-US","@id":"https:\/\/www.ammoman.com\/blog\/#\/schema\/logo\/image\/","url":"https:\/\/www.ammoman.com\/blog\/media\/favicon-152.png","contentUrl":"https:\/\/www.ammoman.com\/blog\/media\/favicon-152.png","width":152,"height":152,"caption":"AmmoMan.com"},"image":{"@id":"https:\/\/www.ammoman.com\/blog\/#\/schema\/logo\/image\/"}},{"@type":"Person","@id":"https:\/\/www.ammoman.com\/blog\/#\/schema\/person\/9da785d0ad23a192dbbca7720dba0b58","name":"Kevin Creighton","image":{"@type":"ImageObject","inLanguage":"en-US","@id":"https:\/\/www.ammoman.com\/blog\/#\/schema\/person\/image\/","url":"https:\/\/secure.gravatar.com\/avatar\/6919163eaa23ebc998f38e1d12e06f06c51c978c16705b623b7e10df3a675902?s=96&d=mm&r=pg","contentUrl":"https:\/\/secure.gravatar.com\/avatar\/6919163eaa23ebc998f38e1d12e06f06c51c978c16705b623b7e10df3a675902?s=96&d=mm&r=pg","caption":"Kevin Creighton"},"description":"Prior to joining the team at Ammoman.com, Kevin Creighton led the marketing for a number of companies in the firearms world. 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