Frequently Asked Questions:  STS Rifles





Here are a few answers to our most frequently asked questions about STS Arms Rifles:

What is so great about an STS Arms rifle?
STS Arms rifles start with the same (or better) high quality component parts as other AR platform rifles.  However, this is where the similarities end.  Parts at STS get completely refinished in Cerakote or Microslik (depending upon the use) to improve performance and corrosion resistance at every level of use.  Coatings are optimized to ensure your STS rifle will still be running when the other rifles have already been junked for spare parts.  It is routine for our rifles to run without cleaning for thousands upon thousands of rounds, full-auto (law enforcement or military users only) or semi-auto.  Upgraded models with Enidine buffers and PWS brakes are stabilized at both ends of the rifle for unbelievably silky smooth cycling and shot-to-shot recovery.

How can I get an STS Arms rifle?
If your dealer doesn't already carry STS Arms rifles, he should.  However, you can contact STS Arms directly and request us to get into contact with your dealer.  You can call us at 541-336-3006 or email ron@stsarms.com to order and start the transfer process to your dealer.

If the internals and inside of a firearm are coated won't this ruin the functionality?
STS Arms coatings and processes are not like other coaters.  We do not "glop" on a product and leave the consumer to reassemble his firerarm.  This is why our price quotes include assembly.  We use Cerakote products such as Microslik on a lot of the internal parts to ensure 100% functionality of your firearm.  Cerakote itself is not as thick as other products and is far more conducive to internal coating without failures.  Rest assured, the functionality of your firearm will either be the same or improved from when you sent it to us.  Concerning competition 1911s, the owner of STS Arms is a competition shooter and builder of 1911s and 2011s and knows what it takes to apply Cerakote without affecting functionality of your competition pistol.

STS doesn't make an AR15 rifle with what I want on it.  Can I request custom parts and configuration?
Please visit the products custom rifle page to see what parts we regularly provide for custom builds.  If you want something that is not on those pages, please contact us to find out if we can get those parts for your build.

Does STS do permanent flash hiders to make up the 16 inch legal barrel length?
Yes, we do this for an added charge of $50, plus the cost of the brake or muzzle device (if not already included in the price of the rifle), plus the cost difference in the barrel (if any).  Some barrels shorter than 14.5” can have certain devices permanently installed to make a legal 16” length (as measured from the muzzle to the bolt face with the bolt closed).

How should I clean my rifle?
While STS rifles perform well for extended periods of shooting without cleaning (9,000 rounds), we recommend cleaning after shooting.  Cleaning a ceramic coated firearm uses basically the same process as every other firearm.  We recommend after cleaning to do one of three things to the action of our rifles: either lightly oil, light oil and wipe dry, or completely dry without oil.  You can use whatever method you desire and can vary it based on the environment in which you will be using your rifle.  For best operation, we recommend less oil or dry.  Environmental particulate (dust, etc.) and powder fouling will cling to oily parts much better than dry ones.  If the environment is wet or salt air and you expect to discharge the rifle very little, oiling lightly could be the best alternative to maximize corrosion resistance for the internal parts.

The exterior of the rifle need only be cleaned of dirt, mud, grease, and dust and then wiped dry.  There is absolutely no need to oil Cerakote finish on the exterior of an STS rifle.

Are there cleaning agents I can't use to clean with Cerakote?
No.  There are no cleaning agents which affect Cerakote or Microslik that can be normally obtained for cleaning firearms.  Unlike other spray on finishes or anodizing, sonic cleaners do not affect the finish.  Clean away without any worries.

Is every part of an STS rifle coated?
All the springs, pins, detents and small parts are coated.  On A2 front sight base rifles, the entire front sight base is coated, as well as the sight, detent and spring.  Aftermarket flip front and rear sights and flip sight gas blocks are left uncoated as disassembly is too problematic and cost/labor intensive.  Regular oiling will be necessary for these setups.  Otherwise, all metal parts are coated separately before installation.

Are STS rifles coated under the front sight base?
All STS rifles are coated under the front sight base (unless they happen to be Melonite barrels) and even then, they're likely to have been coated.  Barrels with replacement gas blocks such as low profile or flip front sight base gas blocks are all coated under the base.  This is far superior to the “phosphated under the front sight base” crock of regular high-grade manufacturers.  Under regular firing, the oil is driven from the phosphate, leaving it dry and prone to rust.  This is not so with any STS Arms product rifle.

Why mid-length gas system?
A mid-length gas system has a 9 inch gas tube instead of a 7 inch gas tube (as is standard on carbine models).  The original M16s and AR15s had 20 inch barrels and 12 inch gas tubes.  The advantage to the mid-length gas system is that the overall gas impulse to the action is softened, compared to the 7 inch carbine system.  This results in a smoother operating cycle.  The bolt unlocks slower and some of the violence of the carbine system's unlock/extraction cycle is averted.  The 7 inch gas system was designed for the much shorter barrel of the CAR15 (11.5 inches) and was adopted for the M4's 14.5” barrel as a compromise for standardization.  Because the civilian market has no need for this standardization, the mid-length gas system makes sense as there is actually no downside to this change.

Why not a piston gun or why direct impingement?
First of all, the original AR15's whole action system was designed to not be like other conventional designs of the era.  It was revolutionary in that it combined the gas piston with the bolt carrier to save weight and minimize vibration.  It was called a “direct impingement” system.  Added bonuses were that the inline design minimized recoil eccentricities caused during cycling of the heavy gas piston rods and this also resulted in better accuracy potential.

Certain people in the firearms industry have decided the initial design was flawed and that it could be retrofitted with a gas piston system.  The flaw cited is unreliability of extraction and excessive powder fouling.  There are two problems with this reasoning.  The first is that retrofitting a system not originally designed as a conventional piston system is bad idea just from an engineering viewpoint.  The second is that the unreliability cited was due to an inadequate extractor spring for the speed of extraction common with carbine gas systems.  The spring was good for the speed of the original rifle systems, but lacks the strength for reliable extraction in a carbine system.

STS has solved both issues with two things: extractor upgrades and advanced coatings on the bolt and carrier.  Reliable extraction is achieved through the upgrades to the extraction system.  Powder fouling issues (if they can be termed that) are solved by the ceramic coatings used by STS in that the fouling doesn't stick nearly as well to the coating as it does to bare phosphated steel.  STS rifles routinely make it past 2,000 rounds without cleaning and test rifles have achieved 9,000 rounds without failure and without cleaning or lubricant.  These solutions retain all the advantages of the original impingement design while solving the minor reliability issues.

What is direct impingement?
“Direct impingement” is the system originally designed by Eugene Stoner for the AR10/AR15/M16 system later adopted by the United States military.  It is called such because high pressure gases siphoned from the barrel during discharge of the firearm is piped directly back into the action system to fill a chamber designed to mechanically expand during the action cycle.  The chamber, as it expands, pressed the bolt forward in the carrier, which causes it to rotate and unlock from the barrel extension.  Because the bolt and barrel do not move forward, the bolt carrier moves rearward.  The carrier moves so fast rearward it is then impelled against the action spring, moving fully rearward.  The bolt is attached to the carrier so it goes with the carrier and does the job of extracting the spent cartridge case, ejecting said case, then stripping off a new round of ammunition (on its forward trip).  The direct impingement of this system is termed such because the actual piston of this system is integral with the bolt and carrier system.

What is gas piston?
In a gas piston system, gas is siphoned from the barrel during firearm discharge, piped into a chamber which has at one end something resembling an internal combustion engine's piston.  It is piston shaped on one end and is rod-like for the rest of the part.  The piston is contained in a tube or other capturing type design, spring loaded for return to position.  During the firing cycle, it is driven at high speed back into the bolt carrier to drive the action open.  This tends to be a very violent process with one heavy steel part hammering on another.  The gas is regulated so that the bolt carrier doesn't move rearward too fast for the bolt and extractor to do its thing.  Because the piston can have so much more control over gas pressure curves, it is easier to regulate the speed of the action cycle.

Why does STS recommend Enidine buffering systems?
Enidine AR-restor buffering system replaces the normal action buffer inside the receiver extension (buffer stock tube).  ITT Enidine company specializes in vibration reduction systems.  Applied to the AR15 platform, the Enidine buffer reduces overall vibration of the action cycle.  The bolt carrier doesn't slam into the rear of the receiver extension at the rearmost portion of travel and this reduces the felt recoil and helps to stabilize the forward travel of the bolt carrier group.  Stabilizing the forward travel makes for more reliable feeding and completely eliminates the “bolt bounce” when the firearm action closes.  This bolt bounce is an issue on full auto rifles due to the hammer being released just as the bolt closes.  Bolt bounce also is not conducive to accuracy as the bolt is closing erratically.  Upon extraction, the Enidine reduces the speed of action opening-reducing the overall violence of the carbine gas system.

Why does STS use Primary Weapons FSC556 brake?
STS Arms has found that the Primary Weapons FSC556 brake is the most effective combat flash hiding brake currently available.  It has proved to stabilize the muzzle movement of a wide range of barrel lengths, keeping the sights on target throughout the recoil cycle.  It is well constructed and shows no signs of wear in extended usage.

What is the advantage to Melonite (salt bath nitride) barrels?
Salt bath nitride (Melonite, Tennifer) is a dip process metal treatment which hardens the surface of steel and provides a highly corrosion resistant finish.  It turns out black.  The surface hardness for QPQ process is 70 RC (comparable to hard chrome).  The process results in less than 0.0001” dimensional change.  It is overall, superior to conventional chrome lining due to two factors.  First, the thickness of the hardness is 0.005” whereas chrome is deposited 0.0003-0.0005” thick.  Second, due to the lack of dimensional change, salt-bath nitride doesn't affect accuracy.  Competitive bench rest shooters are beginning to use salt-bath nitride to improve effective barrel life.  Salt-bath nitriding lasts longer than chrome lining.  There is some debate about salt-bath nitride not holding up as well for belt-fed machine gun purposes.  So, if you're using one of those, you might look into something other than just bare Melonite.
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