AR Gun Barrel Composition

A) Melonite Barrel is a thermo chemical treatment that improves surface hardness properties. This makes a surface that is extremely hard infused steal. Melonite is not a coating but an infused surface hardening process in a heated liquid salt bath. The surface is then 100% harder (62-72 on the Rockwell hardness) than before treatment. It is good at withstand corrosion heat and abuse. See (B) below

B) Iron Nitride barrel. Nitric acid is used as a surface hardener and like Melonite creates a hard outer crust on the steal. This crust is not very thick in Melonite or nitric acid hardening but is very hard and ware resistant. Though it is not clear concerning the Melonite process it is a molten salt bath which requires a good amount of heat to preform. Around WWI liquid salt baths were common place one used liquid potassium nitrate as part of the bath and the barrel was then put in an oven under controlled heat to finish the process. Nitric acid hardening is called low heat hardening and the part is dipped in nitric acid and then heated to the desired heat to give the surface an extremely hard Iron Nitride thin crust. Which is best Melonite or Iron Nitride is unclear as I am unaware of comparative testing.  Some say however that they are both about the same. But I do not know?     

C) Chrome Moly Barrels (Not chrome lined) Around WWI and into WWII steel was being developed of superior nature and this was done by adding chromium and molybdenum to the mix this gave a stronger and harder product for military rifles. Today it might be called 4140 steel or there about depending on the scale used. By today’s standards it is a cheaper product and labeling it as chrome moly people think they are getting a chrome lined barrel when they are not. This does not make it bad stuff it is just not as durable

D) Chrome lined barrel—This is considered by many as the most durable barrel and will shoot the most bullets- - out lasting other gun barrels. Some claimed a slight loss in accessory. This is the most desired barrel.
E) HBAR barrel- This is a Heavy Barrel Automatic Rifle 15- which  is a Match grade barrel which is exclusively guns for target shooting and competition shooting and is perhaps the most accurate barrel of the AR line. The down side is the extreme weight of the gun and the necessity for something to set it on to shoot it. Not a good bush gun for hunting!  

E) Rapid fire and gun barrel life no matter which gun barrel you have you need to take the time to not get it to hot. In a war of course you may have no choice than to shoot a lot of bullets in a short period of time but shooting a number of clips of ammo on rapid fire can according to Gun smiths cost you 1,000 rounds of barrel life each time you do it.

 Gun Barrel Steal – This is created by an emulsion of steal or a better term is to mix chromium and steal in the manufacturing process. People think it is like your kitchen cook ware stainless steal pots which is not so! People think it needs less care which is not so! People think it is as strong as steal which is not so! While taking the instructors course for concealed carry one policeman spent some time talking about the misconceptions of stainless steal gun parts and guns. 1) Stainless is weaker than steal as the emulsion is not as pure and mixed as finely as dairy stainless. 2) The problem of Stainless steal gun barrels is the amount of chrome added creating the mix and creating molecular gape making the steal not as strong, 3)A Stainless steel gun needs more care in cleaning especially under the grips of hand guns and in gun barrel cleaning in rifles and pistols because of the molecular gaps allowing corrosion.

 I Have a precision machining certificate so I can discuss metal kind of intelligently though I do not know all the refining processes in their entirety I can explain a few.

As in any process the right amount of products can be useful and the overabundance of some products can have a detrimental effect.

Nickle – an element used in steal in some gun barrels.  

Chromium – an element used in some gun barrels steel but not enough to create stainless steel. The other use is to chrome line a gun barrel which is the most desired gun barrel to own.

Tungsten—This product is too hard for gun production and would take a lot of heat to create a gun barrel let alone rifle one. Tungsten rings are sold today and you are warned that if you ever crush one on your finger you will need to cut your finger off to get it off as cutting tools will not cut it. Tungsten is a metal cutting tool in a machine shop. Christensen arms clams a  CA 10 –308 caliber tungsten rifle but only mentions a carbon wrapped match grade barrel.

Titanium as an alloy in steal in small quantities can be useful but as a gun production product it has many problems such as Titanium barrel with a steal liner—Such barrels are sold manly for pistols and Titanium receiver parts but offer no real use other than making a much lighter gun. The downside of making such guns is the fact that they need a steal liner in the gun barrel and when the gun is lightened to much there is a great loss of accuracy from recoil. Titanium is thought of as corrosion resistant as the US military makes our submarines out of it. The fact is that it is very susceptible to corrosion and a submarine would sink in a few days if it did not have a coating of 3 inches of rubber protecting it from the salt water. I would not own a titanium gun or gun part under any condition unless it was free. Titanium is a gummy product when it is machined so on ware parts or parts that rub in movement we would have to expect this gummy nature to be present from friction and heat.  

Nickle—useful as an alloy in a gun some barrel.

Non Metallic products useful in steel production.

Sulphur – generally a trace element in steal.

Molybdenum in describing gun barrels it is called Moly and when a small amount of chromium is added to the steel the gun barrel is called a Chrome Moly gun barrel.

Carbon is removed from molten iron makes a brittle product when the carbon is removed you end up with steel and the right amount of carbon is added so the steal can be hardened after the machine work is preformed to make a part.

Silica or sand--A small amount of sand or silica is added to help in not only binding but cleaning the steal when it is melting. In ancient crucible steal the mix was sand, steal scraps or ore and carbon in a mud furnace and a full days work of pumping air into the mud furnace and jamming in charcoal and another pounding the steel to make a fine knife or sword. Followed by weeks of finish work. Silica today is added according to amount needed and nothing more.

Richard W. Norman    American Handbook on Guns Ammo and Freedom