Our Reader Feedback feature allows us to facilitate discussion between Heat Treat Today‘s content contributors and hard-working folks in the shop who have questions about an article.

This Reader Feedback exchange followed an inquiry to our publisher Doug Glenn about government regulation of heat treatment of firearms which we threw out to a few of our consultants and individuals who have knowledge and expertise in this field — and we added a few questions of our own. Our experts are Doug Shuler, lead auditor with Pyro Consulting LLC; John Quaglia, president of Bennett Heat Treating and Brazing; and Jamie Jones, president of Solar Atmospheres. If you have any questions about this or other topics you’ve seen covered on any Heat Treat Today platform, please submit them to editor@heattreattoday.com.

Do you know if any type of firearms license is required to heat treat firearm components?

Doug Shuler: It depends on which components are being heat treated.  Barrels, slides, etc. do not require a license, but if the receiver (the part with the serial number) is heat treated, a license is required and the heat treater is subject to ATF audits. . . . Basically, if serialized parts are heat treated it must be done under an FFL (Federal Firearms License) so the ATF can audit the whereabouts of any firearm at any time.

John Quaglia:  To the best of my knowledge, based upon some pretty extensive experience heat treating firearm components for one of my customers, the only license I am aware of is an FFL which is required to heat treat serialized receivers. If the components are military or ITAR controlled, you must be registered with the DDTC and have ITAR certification, [as well as] for domestic (commercial firearms) if you are heat treating serialized components of a firearm (the receiver). Barrels, slides, sights, magazines, springs, firing pins, etc., are all easily acquired and interchangeable between firearms and therefore require no special permitting.

Jamie Jones: The US Department of Justice authorizes the ATF to regulate those who are manufacturers, dealers, collectors, and importers of firearms and destructive devices. Part of that regulation requires a license (Federal Firearms License [FFL]) be applied for and held by those who are involved with any of the above. For a contract heat treat company, this essentially only pertains to serialized components. Under the “manufacturing” definition, the ATF considers any activity which results in the manufacture of firearms for sale or distribution (including installing parts in or on firearm frames and receivers, and processes that primarily enhance a firearm’s durability), constitutes firearms manufacturing, and requires a manufacturer’s license.  The FFL does not include components related to fully automatic firearms or suppressors.  In order to possess and process those serialized items, the ATF requires a manufacturer’s FFL plus a special occupational tax stamp (SOT).  Prior to issuance of the FFL, the ATF will conduct an on-site audit of the operation and person(s) applying for the license/stamp.  The FFL needs to be renewed every three years.

What is the most challenging part of heat treating gun parts?

JQ: Managing distortion is probably the most challenging as most components are very close to being finished machined. Special racking and methodizing is often required. Marquenching, ausquenching, and vacuum processing are often employed to minimize or eliminate the possibility of distortion. Also, due to the small size and complex geometry present, inspection of the parts is difficult. It is important to clarify the testing location with the manufacturer prior to punching hardness holes into areas of the parts that may be exposed after assembly. After all, manufacturers want their guns to look nice afterward. We have experienced delayed rusting on barrels due to the combination of steel wire and the 4150 barrel reacting to cause anodic corrosion after processing in a salt bath which would only expose itself after a few days. We would ship parts that were perfect, and two days later I would be on the phone with my customer trying to explain a mysterious rust line through the rifling in the barrel. We solved this with some tooling changes.

JJ: Frankly, it is no more challenging or different than heat treating any other parts for any other industry. Some parts are routine and some are challenging. Some materials are more challenging than others and some designs are more challenging than others.

Which parts are the most difficult and why?

JQ: They all present challenges. Slides and barrels present challenges due to the non-symmetrical nature which require special setup procedures. These also tend to have lots of crevices and blind or small holes which trap quenchants, salts, cleaning materials which tend to lead to unhappy customers unless the parts are thoroughly cleaned. Magazines present challenges because they are thin steel stampings which tend to distort due to the quench and induced stressed relieving themselves during heating. I could write a book on the challenges we have faced with the processing of gun parts.

JJ: Parts that require carburizing which have been machined to a finished or near-finished state, with intricate designs, cut-outs, and varying cross sections are the most challenging; a perfect example of this is an AR bolt carrier.  This kind of challenge is why we developed our version of low-pressure vacuum carburizing, as we now don’t need to worry about severe quench distortion or carbon potential control. With traditional carburizing, the austenitizing temperature of the steel can change if too much carbon diffuses into the corners and edges.  This can lead to retained austenite and carbide formation.  Our process negates that phenomenon by using precisely controlled boost-diffuse controls instead of carbon potential.  Our process also leaves the parts bright, with no post carburizing blasting or cleaning operations required.

Is it the materials that make it difficult or is it the configuration of the part?

JQ: The materials tend to be common that most heat treaters have worked with before so from a metallurgical standpoint I would say that the materials are not the problem. The configuration of the parts is definitely worse. Non-symmetrical parts tend to distort more than symmetrical parts. It also makes it difficult to inspect the parts. Test in the wrong area and you have spring-back or rocking. As I mentioned earlier, if you test in the wrong area the customer cannot sell the part. Some gun manufacturers have test methods that are unconventional, testing a shallow case depth using an HRC scale, so that the hardness reading is a combination of the case hardness, case depth, and core hardness.

JJ: It seems like you are assuming it is difficult all of the time! Please see my answer to question 2 above.

Are there any other special processes or regulations that need to be followed when heat treating gun parts? If so, what are they?

JJ: This answer is not to be taken as legal advice. If you want to apply for an FFL, or you get an FFL, you need to know the regulation. It is serious business: if you don’t follow regulation, you could end up in prison. You need to keep detailed records of EVERY serialized component that you receive, process, and ship. You don’t want to be on the tail end of a missing part or parts, especially if you don’t know about it. If something goes missing you need to report it immediately. Of course, reporting it could mean losing your license. So my advice to anyone considering this is: BE GOOD AT TRACEABILITY and RECORD KEEPING!

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