By Wayne van Zwoll<\/a><\/p>\n N<\/span>ot long after the U.S. Army approved the M16 for service rifle matches in the 1990s, gunsmith Bill Wylde of Greenup, Illinois, decided to fashion a rifle chamber that would manage the pressures of the frisky 5.56 NATO but deliver the superior accuracy of bolt rifles bored for the .223 Remington.<\/p>\n The .223 Wylde is not a cartridge. You\u2019ll not find .223 Wylde ammunition. The .223 Wylde is in raw form a series of dimensions. In finished form, it\u2019s a chamber with those dimensions.<\/p>\n A review of the .223 and 5.56 NATO makes Bill Wylde\u2019s inspiration easier to understand. These twins date to 1957, when the .223 emerged as an experimental cartridge for the new AR-15<\/span> infantry rifle. Gene Stoner and Bob Hutton at\u00a0Guns & Ammo<\/em>\u00a0magazine paired a 55-grain bullet with a case slightly longer than the .222\u2019s. Given an exit speed of 3,250 fps, that spitzer met the Army\u2019s requisite of supersonic flight to 500 yards.<\/p>\n The new load was adopted in 1964 as the 5.56mm Ball cartridge, M193, and accompanied U.S. forces to Vietnam. In 1980 it earned a nod from NATO, which substituted an FN-designed 62-grain SS109 boat-tail bullet at 3,100 fps. Its superior ballistic coefficient brought more and harder hits at distance. Faster 1-in-7 rifling twist maintained accuracy. The U.S. Army called this load the M855. Case length in millimeters established the name: 5.56\u00d745 NATO.<\/p>\n Remington led the rush to chamber for it in sporting rifles. The .223 owed much to the popularity of the .222 Remington, introduced in 1950. The \u201ctriple deuce\u201d dominated at Benchrest meets, and was soon the darling of \u2018chuck, crow and fox hunters. While the .223\u2019s 1.760-inch case was only .060 longer than the .222\u2019s, the .223\u2019s had a short neck and held 20 percent more powder. Springfield Armory and Remington had rejected a 1.850-inch hull as a trifle long for the AR-15<\/span>\u2019s action. In 1958 it found a commercial home as the .222 Remington Magnum, first offered in the Model 722 bolt rifle.<\/p>\n Before diving into an exacting description of what the .223 Wylde is, let\u2019s take a look at the .223 Rem and 5.56 NATO.<\/p>\n It\u2019s easy to see why the .223 and 5.56\u00d745 NATO are commonly thought to be interchangeable, if not identical cartridges. (Be sure to read our .223 vs 5.56 article<\/a>.) Listed case dimensions are the same, and each will fire in chambers bored for the other. But there\u2019s more to the tale, and \u201cthe rest of the story\u201d is why the .223 Wylde is important.<\/p>\n Numbers can enlighten. SAAMI specifies .223 Remington loads be held to 55,400 Copper Units of Pressure, while service loads for the 5.56 NATO can generate 58,500. CUP measure has deep roots and is taken this way: A copper cylinder of fixed dimensions is placed over a hole in the barrel wall above the chamber; firing a shot compresses the copper; a measure of the compression converts to units of pressure.<\/p>\n More recently, a transducer or strain gauge is used to register pressure over small slices of time, yielding a pressure\u00a0curve<\/em>\u00a0in pounds per square inch. CUP and PSI values are often carelessly traded, one for another,\u00a0but<\/em>\u00a0they are not the same! Nor is there a formula to convert one to the other.<\/em>\u00a0Maximum average pressure for the .223\u00a0in PSI<\/em>\u00a0is 55,000. It\u2019s 62,000 for the 5.56. Not the neat mathematical relationship you might expect, given their CUP values! Even if a handy conversion formula existed, the\u00a0location\u00a0<\/em>at which these measures are taken on the .223 and 5.56 cases preclude easy comparisons.<\/p>\n Bear with me. In SAAMI\u2019s lab, pressure is taken near the middle of the case. NATO hews to the C.I.P. or European practice of tapping pressure at the case mouth. Mid-case pressure for a 5.56 load at the 62,000-psi ceiling is 60,000 psi\u2026 Lost in this numerical fog, you\u2019re left with a pretty simple conclusion: Standard 5.56 loads are frothier than those for the .223. This doesn\u2019t mean 5.56 cartridges fired in a .223 chamber will shred the barrel \u2014 only that .223 rifles aren\u2019t required to brook proof pressures at 5.56 levels. Many .223 rifles can easily withstand the battering of 5.56 rounds, and function smoothly \u2014 just as Uncle Willard\u2019s weary \u201906 submits to handloads hurling 150-grain bullets at Mach 3.<\/p>\n Live The Armory Life.<\/strong> The latest content straight to your inbox plus an automatic entry to each of our monthly gun\u00a0giveaways!<\/strong><\/a><\/p>\n<\/p><\/div>\n<\/p><\/div>\n Gas from the burning powder builds quickly to uncork a bullet. Its release puts a small dimple in the pressure curve; but the bullet\u2019s easy travel through the throat is over in a trice. When rifling bites into its shank, the bullet slows; gas must suddenly work to keep it moving. There\u2019s a pressure spike. You\u2019ll see that spike when measuring pressure in CUPs only if it exceeds the pressure that started the bullet, as a copper crusher shows only the highest pressure. Theoretically, you won\u2019t know which peak registers, or consequently, if it\u2019s within SAAMI or CIP spec.<\/p>\n More obvious early on was the difference in accuracy between rifles chambered in .223 and 5.56. When Remington began boring barrels and developing loads for the .223, it specified a shorter throat and steeper leade than was standard for infantry rifles. A rodent out yonder begged precision not required on the battlefield. The soldier\u2019s priority was\u00a0function.\u00a0<\/em>His rifle had to cycle reliably under harsher conditions than endured by most hunters. No matter the dust and debris, the water, snow and ice, the palm-blistering barrel temperatures, the condition of the ammunition, a soldier had to have a gun that would run! The generous throats ensuring he could weren\u2019t much help herding those bullets into tiny knots.<\/p>\n Are 5.56 rifles beefier? No. They operate comfortably with ammo that generates higher pressures than does the .223 because chambering reamers for the two cartridges differ.<\/p>\n Base to mouth, the two cartridge cases are identical. They headspace the same, too. That is, from bolt face to point of chamber contact with the case shoulder (datum line), headspace specs are the same. Gunsmiths check headspace with \u201cgo\u201d and \u201cno go\u201d gauges. A \u201cgo\u201d gauge is typically .004 to .006 shorter than a \u201cno go\u201d gauge for rimless bottle-neck cartridges. The bolt should close on a \u201cgo\u201d gauge but not on a \u201cno go\u201d gauge. Usually, if the bolt closes on a \u201cno go\u201d gauge, the barrel is best set back a thread, then re-chambered to achieve proper headspace. However, many chambers that accept \u201cno go\u201d gauges are still safe to use. A \u201cfield\u201d gauge has been employed to check these (mostly military) chambers. It\u2019s about .002 longer than a \u201cno go\u201d gauge.\u00a0<\/p>\n Dimensional drawings show chambering reamers for the .223 and 5.56 are almost identical to the fourth decimal point over most of their length. Thus, the chambers are as evenly matched:<\/p>\n But between the chamber mouth and full-depth rifling in the bore, these chambers differ.<\/p>\n No matter the load, a .224-diameter bullet has less wiggle room as it leaves the case mouth in a .223 chamber than when launched in a 5.56. And it meets full-depth rifling sooner. Pressures in the 5.56 case, higher by spec, would stay higher or peak again more dramatically in the relatively short, tight .223 throat than in the generous 5.56.<\/p>\n Bill Wylde figured few shooters enjoyed fretting over leade angles, secondary pressure peaks and fourth-decimal chamber dimensions. So, he came up with a reamer that enabled any rifle to cycle breezily with both .223 and 5.56 factory ammo\u00a0and<\/em>\u00a0deliver the accuracy bolt-rifle shooters got with their .223s. A Wylde reamer from Pacific Tool and Gauge or Manson Reamers looks like this up front:<\/p>\n Freebore diameter, at .2242, is essentially equal to that of the .223. But at .078, the\u00a0length\u00a0<\/em>of this section is even greater than that of the 5.56. Throat-and-leade length almost matches the 5.56\u2019s. The leade angles are nearly identical. The Wylde\u2019s barely-over-bullet-diameter freebore keeps a tight leash on bullet wiggle upon exit, while a long throat section and gentle leade angle keep pressures at bay.<\/p>\n Incidentally, a Wylde chamber is a bit more generous\u00a0behind<\/em>\u00a0the throat, too: .3572 diameter at the shoulder, .2568 diameter at the neck, .2558 at the mouth. Why? \u201cMaybe to clean up chambers,\u201d suggested a friend. This explanation is appealing not just because it\u2019s simple. It also makes sense. A Wylde chamber can of course be cut in a new barrel. But it can also be reamed from a .223 chamber. Reamer wear, also variations in the practices and workmanship of tooling operators, can produce chambers out of spec, even out of round. The first job of any chambering reamer \u2014 like the \u201cdo no harm\u201d caveat for physicians \u2014 is to ensure any change is positive and doesn\u2019t simply compound a problem.<\/p>\n This review owes much to several smart, experienced people in the shooting industry: rifle-maker D\u2019Arcy Echols, Dave Kiff at Pacific Tool and Gauge, barrel-maker John Krieger, Dave Manson (Manson Reamers), also ace gunsmiths Patrick Sweeney and Fred Zeglin (4D Reamers). Errors are mine.<\/p>\n I\u2019ll own most subsequent confusion around the Wylde chamber too, but not all of it. Some must be laid to reckless use of \u201cthroat,\u201d \u201cleade\u201d and \u201cfreebore\u201d by the brethren, and to variation in measurements. Tolerances also contribute, one reamer, lathe, barrel and operator to the next\u2026<\/p>\n Few truly useful ideas hinge on accurate measures to the fourth decimal. Bill Wylde\u2019s does not.<\/p>\n Editor\u2019s Note: Please be sure to check out The Armory Life Forum, where you can comment about our daily articles, as well as just talk guns and gear. Click the \u201cGo To Forum Thread\u201d link below to jump in and discuss this article and much more!<\/em><\/p>\n Go to forum thread<\/a><\/p>\n
![\"SAINT](\"https:\/\/www.thearmorylife.com\/wp-content\/uploads\/2022\/07\/STAE918223CB-R-Scope.jpg.webp)
\n<\/picture>![\"target](\"https:\/\/www.thearmorylife.com\/wp-content\/uploads\/2022\/07\/9PasteBigTgt.jpg.webp)
\n<\/picture>Are They the Same?<\/h2>\n
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\n<\/picture>![\"hunting](\"https:\/\/www.thearmorylife.com\/wp-content\/uploads\/2022\/07\/4MTgirlPrn.jpg.webp)
\n<\/picture>![\"\"\/](\"https:\/\/www.thearmorylife.com\/wp-content\/themes\/thearmorylife\/img\/logo-tal-tm-icon.svg\"){kind=icon}
<\/p>\nVisible Variables<\/h2>\n
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\n<\/picture>![\"223](\"https:\/\/www.thearmorylife.com\/wp-content\/uploads\/2022\/07\/6VTloadMagV.jpg.webp)
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\n .223 Rem<\/strong><\/td>\n 5.56 NATO<\/strong><\/td>\n<\/tr>\n \n Diameter at shoulder<\/td>\n .3553<\/td>\n .3553<\/td>\n<\/tr>\n \n Shoulder-to-neck angle<\/td>\n 23 degrees<\/td>\n 23 degrees<\/td>\n<\/tr>\n \n Neck diameter at shoulder<\/td>\n .2550<\/td>\n .2551<\/td>\n<\/tr>\n \n Mouth diameter<\/td>\n .2540<\/td>\n .2540<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/figure>\n \n\n
\n .223 Rem<\/strong><\/td>\n 5.56 NATO<\/strong><\/td>\n<\/tr>\n \n Throat length (freebore ahead of mouth)<\/td>\n .040<\/td>\n .070<\/td>\n<\/tr>\n \n Throat diameter<\/td>\n .2240<\/td>\n .2265<\/td>\n<\/tr>\n \n Leade angle (from throat to full-depth rifling)<\/td>\n 3 degrees, 10<\/td>\n 1 degree, 13<\/td>\n<\/tr>\n \n Total throat and leade length<\/td>\n .103<\/td>\n .339<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/figure>\n Where It Counts<\/h2>\n
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\n Throat length (freebore ahead of mouth)<\/td>\n .078<\/td>\n<\/tr>\n \n Throat diameter\u00a0<\/td>\n .2242<\/td>\n<\/tr>\n \n Leade angle (from throat to full-depth rifling)<\/td>\n 1 degree, 15<\/td>\n<\/tr>\n \n Total throat and leade length<\/td>\n .307<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/figure>\n ![\"SAINT](\"https:\/\/www.thearmorylife.com\/wp-content\/uploads\/2022\/07\/STAE918223CB-L-Scope.jpg.webp)
\n<\/picture>Conclusion<\/h2>\n
Join the Discussion<\/span><\/h5>\n
Featured in this article<\/span><\/h5>\n
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\n\t\t\t\t\t![\"SAINT\u00ae](\"https:\/\/www.thearmorylife.com\/wp-content\/uploads\/2021\/12\/product-saint-edge-atc-series.jpg.webp\"\/)
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<\/p>\nSAINT\u00ae Edge ATC Series<\/span><\/h3>\n
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