March 23rd, 2016

Metal Properties Revealed in ‘Guide to Gun Metal’

Sweeney Guide to Gun Metal

4140, 4150, 316, 17-4, 6061, 7075-T6 — What is the significance of these numbers? No, they’re not winning lottery numbers. These are all designations for metals commonly used in firearm and barrel construction. 4140 and 4150 are carbon steels, with 4150 often used in mil-spec AR15 barrels. 316 and 17-4 are grades of stainless steel. 316 is “marine grade” stainless, while 17-4 has 17% chromium and 4% nickel. 17-4 is a harder steel used in barrels and receivers. 6061 and 7075-T6 are aluminum alloys. 6061 is “aircraft grade” aluminum, often used for rings and trigger guards, while 7075-T6 is a much stronger, heat-treated aluminum commonly used in AR15 uppers.

Sweeney Guide to Gun MetalYou can learn about all these metals (and more) in the online archives of RifleShooter magazine.

Written by Patrick Sweeney, RifleShooter’s Guide to Gun Metal summarizes the primary types of steel and aluminum used in gun and barrel construction. Sweeney explains the nomenclature used to define metal types, and he outlines the salient properties of various steel and aluminum alloys. This is a useful resource for anyone selecting components or building rifles. We recommend you print out the page, or at least bookmark it.

Metals by the Number
The number system for steel classification came from the auto industry. Sweeney explains: “The Society of Automotive Engineers uses a simple designating system, the four numbers you see bandied about in gun articles. Numbers such as 1060, 4140 or 5150 all designate how much of what [elements are] in them. The first number is what class—carbon, nickel, chromium, and so forth. The next three numbers [list other elements in the alloy]. 4140, also known as ordnance steel, was one of the early high-alloy steels. It has about 1 percent chromium, 0.25 percent molybdenum, 0.4 percent carbon, 1 percent manganese, around 0.2 percent silicon and no more than 0.035 percent phosphorus and no more than 0.04 percent sulphur. That leaves most of it, 94.25 percent, iron.”

Aluminum Alloys
Numbers are also used to differentiate different types of aluminum alloys. Sweeny writes: “Aluminum is used in firearms in two alloys: 7075 and 6061. 6061 is commonly referred to as ‘aircraft aluminum’ and has trace amounts of silicon, copper, manganese, molybdenum and zinc. 7075 is a much stronger alloy and has markedly larger amounts of copper, manganese, chromium and zinc.” 7075 Aluminum has significantly better corrosion resistance, and that’s why it is used for AR receivers. The “T6″ you often see appended to 7075 refers to a heat-treating process.

Aluminum (or “Aluminium” in the UK) is a chemical element in the boron group with symbol Al and atomic number 13. It is a silvery-white, soft, nonmagnetic, ductile metal. Aluminum is the third most abundant element, and the most abundant metal, in the Earth’s crust. (Wikipedia)

Aluminum alloy table chart Silicon Maganese Zinc Copper Magnesium

To learn more about the metals used in your firearms’ barrels, rings, receivers, and internal parts, read Sweeney’s article in RifleShooterMag.com. Taking the time to read the article from start to finish will expand your knowledge of metal properties and how metals are chosen by manufacturers and gunsmiths. CLICK to Read Guide to Gun Metal.

Story Tip by EdLongrange. We welcome reader submissions. Aluminum Alloy chart courtesy AluminiumDesign.net.
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January 20th, 2016

Is “Stainless Steel” Really Rust-Proof?

Some folks feel that they don’t have to worry about rust and corrosion on stainless steel barrels, actions, and other components. That’s not really true. “Stainless” is a bit of a misnomer. First, there are different types of stainless steel alloys, with different degrees of rust resistance. 300 series stainless is more corrosion resistant than the 416 stainless commonly used in barrels. The composition (by percentage weight) of 416 stainless is 0.15% carbon, 12-14% chromium and the rest iron. 416 stainless steel lacks the roughly 10% nickel content that makes the 300 series more corrosion resistant in atmospheric conditions. But because 416 handles pressure better and is easier to machine (than 300 series steel), 416 stainless remains the better choice for barrels.

stainless steel barrel Techshooter

Though some grades of stainless are more corrosion-resistent, ALL varieties of stainless steel can rust if they are not handled and stored properly. Forum reader Kells81 observed: “Wanna see some rusted stainless? Go to the big “C” brand store in Ft. Worth. Every stainless gun they have on the used gun rack is rusted.” Tom Easly of TRE Custom explains: “Sweat is very corrosive. Sweat and blood will rust many stainless steels. I hate to handle my guns or drip on them when I sweat. It really helps to just wipe them good with a wet rag, dry and wipe on a light coating of gun oil. I think most stainless barrels are made from type 416 stainless, and it is generally pretty corrosion resistant, but not when exposed to sweat, blood, or chlorates (corrosive priming), and some other electrolytes.”

Forum member Jacob, who is studying materials science at LSU, provides this technical information: “The basic resistance of stainless steel occurs because of its ability to form a protective coating on the metal surface. This coating is a ‘passive’ film which resists further ‘oxidation’ or rusting. The formation of this film is instantaneous in an oxidizing atmosphere such as air, water, or other fluids that contain oxygen. Once the layer has formed, we say that the metal has become ‘passivated’ and the oxidation or ‘rusting’ rate will slow down to less than 0.002″ per year (0.05 mm per year).

Unlike aluminum or silver, this passive film is invisible in stainless steel. It’s created when oxygen combines with the chrome in the stainless to form chrome oxide which is more commonly called ‘ceramic’. This protective oxide or ceramic coating is common to most corrosion resistant materials.

Halogen salts, especially chlorides, easily penetrate this passive film and will allow corrosive attack to occur. The halogens are easy to recognize because they end in the letters ‘ine’. Listed in order of their activity they are: fluorine, chlorine, bromine, iodine, astatine.

These are the same chemicals that will penetrate Teflon and cause trouble with Teflon coated or encapsulated o-rings and/ or similar coated materials. Chlorides are one of the most common elements in nature and if that isn’t bad enough, they’re also soluble, active ions. These provide the basis for electrolytes. The presence of electrolytic solutions can accelerate corrosion or chemical attack.”

CONCLUSION: Stainless steel barrels and components won’t rust nearly as fast as blued steel, but you still have to take precautions — particularly removing sweat and corrosive salts from the barrel. Also, don’t let moisture build up inside or outside of the barrel. We recommend wiping your barrels and actions with Eezox, or Corrosion-X after each use. These are both extremely effective rust-fighters that go on thin, without leaving a greasy residue. (Eezox leaves a clear finish, while Corrosion-X has a slightly waxy finish.) Also store your guns in Bore-Store bags when the guns go in the safe. Bore-Stores wick away moisture, and the synthetic fleece inner surface is treated with rust-fighting chemicals. Bore-Stores also protect your guns against dings and scratches.

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June 28th, 2013

Firearm Finish Comparison Testing in Salt Chamber

When evaluating firearm finishes, one should consider hardness, chemical resistance, lubricity, abrasion resistance, and color. However, none of these factors are as critical as corrosion protection. The average firearm owner deals with corrosion more than any other finish-related problem. Accordingly, when selecting an exterior finish for the metal components of your guns, you should look for a product with superior corrosion resistance. Thanks to Cerakote, we now have some science to help you make that decision….

How well do various firearm finishes resist corrosion?
Watch the video below to find out.

Eight Gun Finishes Tested — With Surprising Results
Eight (8) various finishes are tested, including Blueing, Cerakote, DuraCoat, FailZero, Ion Bond, KG Gun Kote, NiBX, and Phosphate (Parkerizing). Eight metal firearm components (each with a different finish) are placed into the salt chamber to see how long it takes for each finish to show initial signs of corrosion. To provide a baseline for comparison, a “naked” 416 stainless steel barrel was also placed inside the test chamber. The test was started, and for each coating, the time was recorded when corrosion started to appear. FYI, if you thought “stainless steel” can’t rust, think again. The stainless barrel sample (along with the blued metal sample) showed visible corrosion after just 24 hours!

After 24 Hours in Salt Chamber
Cerakote salt chamber corrosion test accurateshooter.com

After 48 Hours in Salt Chamber
Cerakote salt chamber corrosion test accurateshooter.com

After 172 Hours in Salt Chamber
Cerakote salt chamber corrosion test accurateshooter.com

Salt Chamber Testing — 5% Salt Concentration at 95°F
According to ASTM B117-03, the Corrosion Test provides a controlled corrosive environment which has been utilized to produce relative corrosion resistance information for specimens of metals and coated metals exposed in a given test chamber. The salt chamber is set to a temperature of 95 degrees Fahrenheit with a 5% salt concentration. Salt Chamber testing is used to draw a comparison between metals and finishes and does not correlate to a specific number of hours of real world use.

Cerakote salt chamber corrosion test accurateshooter.com

Story tip by EdLongrange. We welcome reader submissions.
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December 17th, 2011

Krieger Raises Barrel Prices at End of December

If you plan to use a Krieger barrel for your next rifle build, better get that order in quickly. Due to a rise in the cost of steel, Krieger Barrels will add $15.00 to the price of a most stainless barrels, starting December 31st. In addition, the price of chrome moly barrels will also increase (typically $25) to become the same price as Krieger’s stainless barrels. (Previously the chrome moly barrels were cheaper than stainless.) The biggest price hike comes with large diameter barrels. There will be a large price hike on over-size diameter barrels ($100 increase on oversize blanks up to 1.450″ diameter.) Krieger says the price changes will “take effect January 1, 2012″, but it also states that price increases would be “implemented” on orders received “after midnight December 30th”. So, to be safe, get your order in before 11:59 pm on December 30th.

Krieger has also announced that it is halting manufacture of 17-caliber barrels as “the tooling on this caliber is too fragile”, and Krieger will no longer offer Custom Engraving. Here is the text of Krieger’s 2012 Price Changes Announcement:

Krieger Barrels — 2012 Price Changes

We [want] to give our customers a “heads up” on price increases to be implemented beginning with all orders received after midnight December 30th. Krieger Barrels has not increased the cost of barrels in two years, and now regretfully we find it necessary to do so. Below you will find a brief description of the changes. Detailed information will be posted as a catalog/website update shortly after Christmas. All price and service changes will take effect January 1, 2012.

Barrel Pricing:
The base cost of most stainless steel barrels will increase by $15.00. Chrome moly barrels will then be the same price as stainless making stainless and chrome moly barrels the same price. [This means the cost of chrome moly barrels will increase $25.00 on average.]

Oversize Diameter Pricing:
Oversize blank diameters up to 1.450″ will increase to $100.00 above the base cost in both stainless steel and chrome moly

Oversize blank diameters greater than 1.450″ up to 2.000″ will increase to $150.00 above the base cost in both stainless steel and chrome moly.

.50 BMG blanks (2.00″ x 36″) will remain the same price in stainless, but chrome moly will increase to the current stainless price.

Muzzle Threads:
We are eliminating the price difference between threading for a timed brake and an un-timed brake. The new cost to thread a muzzle to your machinist drawing or to match the device you send will be $125.00 either timed or un-timed. Fox River Brakes will remain $200.00 installed, and DCM/Service rifle barrels will continue to have no price difference between pre-ban and post-ban models.

Story tip by EdLongrange. We welcome reader submissions.
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January 17th, 2009

SHOT Show Report: Stiller Unveils Four New Actions

Stiller’s Precision Firearms showcased a variety of NEW custom rifle actions at the 2009 SHOT Show. Trust us, this is BIG News for builders of precision rifles, both rimfire and centerfire. Jerry Stiller has released no less than four (count ‘em FOUR) new stainless actions this year. They are all impressive, and we predict the new rimfire actions will sell like hotcakes.

Stiller Precision Actions Predator, 408, 40X

New Custom 40X-Clone Rimfire Action
Stiller Precision’s show-stopper is a new 22 rimfire action based on 40X Remington design. Called the Predator 25X, this 40X-clone will be offered both as a single-shot AND a repeater. This is a much-awaited product. We predict huge demand for Stiller’s rimfire actions. There is nothing else like it on the market. The repeater will be perfect as the basis of a rimfire silhouette action or a “tactical rimfire” gun. Stiller’s rimfire actions cost $800.00 and should be available by mid-2009.

Predator V — RBLP Ejectorless Action
The second offering, sure to be popular, is the new “Predator V” action, described by Jerry as “an affordable BR-style action aimed at the varminter.” It is offered in right bolt, left port only, with a cone bolt and no ejector. It’s optimized for bench use for precision varminting, though it certainly could be used in a 600-yard BR comp gun or F-Class rifle. Jerry tells us: “The Predator V is a RBLP version of our Predator line with a few special features. It has a Sako extractor on a coned bolt with no ejector. There is about a .003″ fit on the bolt with a pinned trigger. The main market is high-performance varminting or benchrest. Shown below is our new ‘full bling’ polished Predator V model featuring a blue-accented Picatinny rail, knob and shroud. It is also available in matte or black finish without rails.” The Predator V is IN STOCK NOW and costs $850.00 with rail.

Stiller Predator V action bling

P-1000 Long Range Action
The third new action unveiled by Jerry Stiller is the strong and versatile new P-1000 long range action. This is a RBLP, right-eject only unit with a beefy a 1.55″ diameter. The stainless P-1000 is offered in both short and long actions, with either .308 or magum bolts. The P-1000 is a very rigid action aimed at the long-range benchrest market. NOTE: the P-1000 short action will eject 284s and the long action will eject magnums such as the 300 RUM. The price for a P-1000 (with rail) is $850.00, and P-1000s should start to ship in late February, 2009.

YouTube Preview Image

New .408 Cheytac Action
Last but certainly not least is Stiller’s new TAC 408 action. This is a new long action with a .408 bolt-face. It is optimized for the .408 CheyTac and similar high-capacity, big-rim super-sized cartridges. This action should prove popular with ultra-long-range shooters. Call Jerry Stiller at (972) 429-5000 for price and availability of the TAC 408 action.

Spec, features, and options for Jerry Stiller’s other stainless and aluminum actions can be found on ViperActions.com.

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