Firearms Reverse Engineering : Best Of Weaponsman


Since the passing of our friend Kevin, AKA “Hognose”  we have been  running a “best of” spot of Kevin’s articles.   Best of being a bit of a misnomer as every thing he wrote qualifies.   We will continue posting Kevin’s writing as a tribute to him and an effort to make sure it always exists some where as  we are alive .


Firearms Reverse Engineering

One thing about the people of the gun: we’re conservative. By that, we don’t necessarily mean that we want 15 carrier groups back, eager to cut taxes and services, or sorry that mandatory chapel was gone by the time we went to college. There are actually card-carrying ACLU members and ivory tower socialists among us, but they’re conservative about their guns. For every reader who’s up to date on polymer wonder pistols, there’s about three who wish you could get a new Python. (The reason they can’t is that they don’t want it $3,500-4,000 bad, which is what an old-style hand-made perfect Python would cost to make today). Or a new Luger. For every one of you guys following the latest in M4 attachments (hey, let’s play “combat Legos!”), there’s a few who’d buy a new MP.44, if they could.

Every once in a while, gun manufacturers decide to satisfy these consumer yearnings with product. Sometimes, they succeed. Sometimes, the 10,000 guys who told them they were down for a semi-auto Chauchat turn into 10 guys who buy one and the businessmen get to undergo the intensive learning lab called Chapter 7 bankruptcy. The question becomes, if you are raising a zombie firearm from the dead: how? Even the original manufacturers tend not to have prints and process sheets for >50 year old products, and if they do, the documents are ill-adapted to the way we do things now. If your original product was made in Hiroshima or Dresden pre-1945, or Atlanta pre-1865, odds are the paperwork burned. If the company went tango uniform even ten years ago, rotsa ruck tracking down the design documents.

So, you’re sitting here with a firearm you know you could sell. You have the rights to reproduce it, because any patents and copyrights and trademarks are either in your possession or expired or defunct. Your problem is reverse engineering. It turns out that this is a very common problem in the firearms industry, and the path is well beaten before you.

Some Examples of Reverse-Engineered Drawings

People can do this with some calipers, a dial indicator, and some patience. Rio Benson has done that for the M1911A1.

Screenshot 2015-04-03 09.58.55

He explains why he thought a new set of documents were necessary in a preface to his document package:

Historically, when the drawings for John M. Browning’s Colt M1911 were first created, there was little in the way of ‘consensus’ standards to guide the designers and manufacturers of the day in either drawing format or in DOD documentation of materials and finishes. For the most part, these were added, hit or miss, in later drawing revisions. Furthermore, due to the original design’s flawless practicality and it’s amazing longevity, the government’s involvement, and the fact that in the ensuing 100-plus years of production the M1911 design has been officially fabricated by several different manufacturers, the drawings have gone through many, many revisions and redraws in order to accommodate all these various interests. These ‘mandated by committee’ redraws and revisions were not always made by the most competent of designers, and strict document control was virtually non-existent at the time. All of this has led to an exceedingly sad state of credibility, legibility, and even the availability of legitimate M1911 drawings today.

He modeled the firearm using SolidWorks 2009, with reference to DOD drawings available on the net, and his own decades of design and drafting-for-manufacture experience. The results are available here in a remarkable spirit of generosity; and if you want his solid models or his help producing this (or, perhaps, on another firearm), he’s available to help, for a fee.

findlay-stenIn a similar spirit, experienced industry engineer David S. Findlay whom we’ve mentioned from time to time, has published two books that amount to the set of documents reverse-engineered  from an M1A1 Thompson SMG and from a Sten Mk II. The limitations of these include that they come from reverse-engineering single examples of the firearm in question, and the tolerances are based, naturally, on Findlay’s experience and knowledge. So his reverse-engineering job may not gibe with the original drawings, but you could build a firearm from his drawings and we reckon the parts would interchange with the original, if his example was well representative of the class.

Nicolaus M1 Garand bookOn the other hand, Eric A. Nicolaus has published several books of cleaned-up original drawings of the M1 Garand, the M1D, the M1 and M1A1 carbines, various telescopes, etc.

Nicolaus’s books provide prints like the Findlay books do, but they’re not reverse engineering. They’re reprints of the initial engineering, cleaned up and republished. Not that there’s anything wrong with that.

Sometimes the Industry needs Reverse Engineering

A perfect example is when planning to reintroduce an obsolete product. Most manufacturers that have been around since the 19th Century never foresaw the rise of cowboy action shooting, but now that it’s here, they want to put their iconic 1880s products in the hands of eager buyers. Or perhaps, they need to move a foreign product to the US (or vice versa). In this case, reverse engineering the product may be less fraught with risk than converting paper drawings which use obsolete drawing standards, measures and tolerancing assumptions. You may recognize this reverse-engineered frame:


If you are exploring a reverse engineering job, there are several ways to do it. The first is in-house with your own engineers. (You may need to ride herd on them to keep their natural engineers’ tendency to improve every design endlessly in check). The next, is to outsource to an engineering consultancy that does this. The third is to use a metrology and engineering company, like Q Plus Labs, from whom we draw that pistol-frame example. They say:

[W]e offer numerous reverse engineering methods and services to define parts or product. Q-PLUS provides everything from raw measurement data to parametric engineering drawings that correspond to a 3D CAD solid model! We also offer reverse engineering design consulting to point you in the right direction.

  • Digitizing & Scanning
  • Measurement Services
  • 3D CAD Solid Modeling
  • Engineering Drawings

In other words, you can go there to have them do, essentially, what Rio Benson did with the 1911 with your product. They can digitize an item from 3D scanning, or they can take a drawing and dimension it from known-good examples. Given enough good examples, they can actually determine tolerances statistically and substantiate them to a level that will satisfy regulatory agencies such as the FAA. (This lack of a range of parts and statistical basis for the tolerances is, in our opinion, a rare weakness in Findlay’s single-example approach).

Reverse engineering has gone from something in the back alleys of engineering or attributed to overseas copycats, to something firmly in the mainstream of modern production engineering.


About Hognose

Former Special Forces 11B2S, later 18B, weapons man. (Also served in intelligence and operations jobs in SF).


  1. I believe one more reason besides a true actual demand is unfortunately due to litigation.A run of a 1911 series 70 I saw a few years back were only able to do the 70 series firing system/safeties by calling it a collectible.I wonder how much other not modern/safety up to date issues result in old school not being made for another generation.

  2. Shawn,of course you can’t fill his shoes,that said,does not mean you cannot leave your own footprints on the path with your site,seems like a good thing to me.A good example for me was the bare bones AR 1000 yard shots,out of my league at moment even with the best of gear,but,well,something to “shoot for”.

    Would hope at some point you get into the home assembler/builder end of the path,those are articles I really enjoyed/could sink me teeth into especially with all the new ways to do it.Yes,I do realize also this will have some “bubba moments”but hell,the Wright brothers had their share of those moments before they,well,took off!

    • The home building stuff is something you will probably get from Howard. I can do it, but I prefer to entrust my AR15 making needs to the colt factory. I’m gonna up the output for the website to a higher level this summer though so you never can tell what I may cook up.

  3. One thing I would recommend you want to build up more readers/comments/discussions is do as Kevin and other sites do,you are a trusted poster your comments get on site when sent,makes for easier discussions/debates/closer to real time.This is one of the reasons I once mentioned hitting Weaponsman site was like a virtual Algonquin Roundtable of scintillating conversation,note sure what Kevins thought was on that comment!

    • We used to do that, then we had the issue of someone posting a couple quality replies, then posting lots of garbage.
      Shawn and I will talk it over, maybe it is time to change it again.

  4. I realize that it can lead to spammers ect. but seems to work well on sites that use trusted posters.I will say at times it can lead to “spirited debates” at times but if basically civil and on topic others can learn from it.That said,was on one site in a “spirited debate” and was getting close to ugly,one poster told us to get a hotel room to which I replied more like we each get a flag and cutlass and fight it out!Site owner said take it private and with our agreement let our e-mails be passed,still talking on line a few years later and hope to meet up one day for a drink.Truly garbage replies and not just uninformed replies can be banished pretty easy depending on how site set up,anyhow,would consider it.

    • yea you are probably right. If or when we do change the comment section, I am going to edit my M14 post and put it as being written by you though James. Let you take the heat for me. You wouldn’t mind helping a fella out would ya? whats a few death threats and motherly insults a day? I’m just kidding though. well unless you tell me its ok.
      The Kevin’s comment section was and is the best commenting group I have ever seen on the web. It was a real pleasure reading and interacting with you guys. I miss that almost as much as I miss him.

      • Not only tis it OK,be glad to take on the comments,that said,m14 knowledge pretty limited,so a warning ahead of time would be good so I don’t come across on replies as a total/slack jawed/drooling troglodyte,consider partial droll acceptable.I would say be a better referee and let the folks hash it out!

        derogatory comments about me old Diamond Rock bow would though lead to expletives/death threats/strange substances in mailed letters ect.!


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