SAR 20#2

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At high heat levels- those commonly encountered in military applications, 416 can distort, lose its heat treated state, and even de-alloy—a condition where the additive materials lose their microscopic bonds to the iron/carbon structure. So this material, while in use, could become unsuitable or even unsafe. Not to worry—416R comes with a reliable programmed response to imminent failure. It will split like a banana peel before it fragments. This splitting action is resultant of the “stringers” as they’re called, the areas of sulfur that co-mingle in-between the regions of martensite (crystalline structures) in the metal alloy. There are other grades of stainless one might encounter in barrel making. 410, 420 and 17-4 are less common, though they are found in use. 17-4 is renowned as a super alloy. It is fabled to get stronger from heat exposure. It has been said that it possesses mystical powers to “self-heal” micro fractures and surface defects. Few have ventured to deepdrill and cut rifling into a chunk of 17-4. Many have failed. The name Noveske will forever be remembered as one that succeeded. 17-4 is mainly used in pistol and revolver frames, muzzle devices, or small parts and even receivers and bolts of custom high-end high-power rifles. The last stainless worth mentioning here is 410 alloy. It is the underachiever of the bunch. The yield of this material is actually less than its intended operating threshold- a fact that some in the industry will argue. 30,000 PSI is where 410 can undergo “plastic deformation,” that is, be stressed past its ability to bounce back. Barrel makers still use this stuff knowing that a 5.56 NATO cartridge reaches over 60,000 psi just after ignition. Is this cause for alarm? Not really. Stress is calculated as a constant applied force. The pressure curve inside a gun barrel in not contained for any period of time, nor at a static load, but rather a burst that reaches a peak pressure. The pressure is not contained long enough or focused at a singular point where it could cause damage to the barrel. The barrel is saved by the fact that high pressure gas acts with equal force on all sides of its container (in this case the barrel)- and one side of the container (the bullet) is moving away from this applied force. So the bullet is effectively a valve that allows the pressure to escape. 410 alloy is said to be tougher and more abrasion resistant than 416. It is used by some manufactures to make gun barrels to save cost as it is imminently easy to machine. The more common stainless, 416R does deliver on some promises. Many custom rifle builders who work for the competition market trust 416R. Countless benchrest, palma and F-class records have been claimed by guns fitted with barrels made from 416R. This material does in fact make for a perfect surface finish during machining. This perfect surface lends itself to superb accuracy. A barrel properly ‘smithed from 416R will perform supremely, though not indefinitely. A match-grade stainless barrel fit to a high-powered competition rifle may be expected to have a good service life of 3000 rounds, more or less, depending somewhat on the caliber of the rifle, and largely on how it is cared for. Steel of any alloy may be encountered in a number of “states.” This refers to the condition of heat treatment it may have received. Annealed steel has been softened. This condition does not imply that the steel is mild- only that it has been reduced to a softer state to make it more workable. Hardened steel generally refers to a surface hardening to improve that steel’s wear resistance or reduce its frictional coefficient. This condition may also be called “case” hardened. Heat treated steel is generally hardened throughout, also known as “core” hard. Core hard is a condition commonly employed on high wear or high load components. Certain alloys are better suited <strong>SAR</strong> Vol. 20, No. 2 84 MARCH 2016
to be case hardened. Others are tailored for use in core hard applications. For example, the bolt carrier group in an AR-15 is made of several steel alloys- each selected for it properties as they fulfill the requirements of the BCG’s operation. The bolt itself may be made of something called Carpenter 158 that has been heat treated to a desired surface hardness to resist wear while maintaining internal elasticity, and resistance to fracture of the locking lugs. The bolt carrier body is commonly made of core hard 8620- a nickel-chrome-moly steel used for its superior resistance to heat induced fatigue and mechanical shock. The carrier houses a high-temp expansion chamber that is usually hard chrome plated. The gas key might be made of 4130CM, and specially coated to resist high temperature and impart lubricity so as not to cause abrasion to interacting surfaces. The cam pin receives tremendous abuse, and is formed from a core-hard piece of 4340CM—very high in nickel and chrome. The cam pin will endure severe abuse- repetitive compressive and shear forces and high heat imparted by the M-16’s operating system. These parts are often protected by a hard metal plating or clad in a metal/polymer matrix. Both, designed to kill friction and resist heat’s damaging effects. So we can conclude that there is no “best” steel for your gun. Lesser materials may be used to great result provided proper engineering and quality assurance to back them up. Super alloys can lose all their attraction when cost and gained advantage are brought into proportion. Long past are the days of Damascus steel when one could be killed by his own gun if the bi-metal structure were to give way. The quality and consistency of steel used in the industry today exceeds the quality of manufacture implemented by the gun makers themselves. Our modern steel industry is nearly flawless. Good steel makes us better. WWW.SMALLARMSREVIEW.COM 85 <strong>SAR</strong> Vol. 20, No. 2
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NEW sa ARMING THE NEW! - Guns of th
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SAR STAFF PUBLISHER Chipotle Publis
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NEW PRODUCTS by Chris A. Choat SAR
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ROGERS HOLSTER OFFERS NEW QD MOUNT
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SAR Vol. 20, No. 2 MARCH 2016 12 TA
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FLASH SUPPRESSOR, MUZZLE BRAKES & M
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ARMING THE GALACTIC EMPIRE 22 22 SA
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E-15 IMPERIAL STORMTROOPER The vene
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License-produced versions meet the
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SAR Vol. 20, No. 2 28 MARCH 2016
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E-15 IMPERIAL STORMTROOPER er so eq
Page 34 and 35: The A*B Arms Modular Weapons System
Page 36 and 37: The author’s Remington SPS 700 ri
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Page 40 and 41: MOD * X + ACCUPOWER ® ABOVE: The s
Page 42 and 43: The Lancer L30 HM (Heavy Metal) & N
Page 44 and 45: With the surge in modern sporting r
Page 46 and 47: ment of a front back up iron sight.
Page 48 and 49: ABOVE TOP: This is the Carbon Fiber
Page 50 and 51: Mossberg MVP LC: HIGH CAPACITY PREC
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Page 56 and 57: it comes to handling due to weight
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Page 60 and 61: CONCEALED CARRY HANDBAGS AVA LOCK C
Page 62 and 63: THE AMT AUTOMAG III BY FRANK IANNAM
Page 64 and 65: AMT AUTOMAG III forward. It should
Page 66 and 67: ful to keep the barrel delay spring
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Page 70 and 71: combat handguns in the modern era a
Page 72 and 73: ABOVE: This representative sample o
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Page 76 and 77: MEANING of the 1920-MARK on GERMAN
Page 78 and 79: a b a. A German submachine gun MP18
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Page 88 and 89: Czech ZB26 17 TOP: First opening an
Page 90 and 91: GUNS BY KYLE SHEA of the SILVER SCR
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