AGI - Products Winchester Model 12 Shotguns

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Winchester Model 12 Shotguns


Winchester Model 12 Shotgun

Step-by-step design function and repair of this gun that from 1912 to 1965 defined the American pump shotgun. Still prized by many, with prices to match, this video course takes you through total disassembly, maintenance, reassembly, and troubleshooting. Everything you need to know to keep this old workhorse operating.

Bob Dunlap is a renowned expert on most of todays and yesterdays important and obscure firearms. He has been a warranty station for most manufacturers, both large and small. He understands the design, function, and repair of firearms in general, and certainly, the gun that was the first truly successful internal hammer gun, and a derivative of a John Browning design.

If you want the quick course on how to get the worlds best loved pump shotgun apart, back together, and operating as intended, then this course is for you (if you want the long course, look into our basic 108 hour Professional Gunsmith Course.)

Among the items covered are:


  • The model 12 was designed by Winchester employee, Thomas Crossly Johnson, and was based in large part on a design by John Browning.
  • Produced from 1912 to 1963, and as limited custom shop guns through 2006. Almost 2,000,000 were made
  • Guns made in take-down and solid frame versions, but the vast majority were take-down
  • Started to lose sales to the Remington 870 in the 1950s because the Remington was perceived to be almost as good and was less expensive
  • Gun was fairly expensive to make, certainly more so than the Remington and Savage pump offerings, and gun was discontinued in the Great 1964 Winchester Debacle
  • Gun feels good, looks good, and is very reliable

Design & Function

  • Gun is a tipping bolt
  • Operation of the locking bolt explained and demonstrated.
  • Action bar operation demonstrated and the reason pump guns through the Ithaca 37 had a Hesitation feature built in is explained
  • Trigger group removed and the action bar lock operation is observed and explained
  • Fire control system operation is explained in detail and shown with extreme close-ups
  • "Slam-Fire" feature defined and shown
  • Firing pin safety operation shown
  • The feeding cycle
  • Cartridge stop operation demonstrated
  • Carrier operation shown
  • Ejector operation shown
  • How to correct failure of the cartridge stop to stop cartridge
  • How to correct the problem if you tried to reassemble the gun with the bolt slightly to the rear
  • How the bolt lock works, and why its there in the first place


  • Extensive disassembly, and instructions on how to take apart those parts/assemblies not disassembled, and explanation of why some assemblies are not to be disassembled
  • Barrel and magazine removal and disassembly
  • How the take-down system works
  • Be careful of the receiver extension! It is fragile and easily broken if you try to remove it without knowing what you are doing
  • How the take-up bushing works to tighten up a loose barrel
  • One thing you never want to do
  • How the forend is removed and a tool to make it easier
  • What to do when the magazine tube is slipping threads and you cannot find a new tube
  • Trigger group and carrier disassembly
  • Bolt removal
  • What the chamber ring is, and why you do not remove it
  • Bolt disassembly
  • You get a good look at how the various parts fit together and interact (particularly the springs) after they are removed from the gun and Bob explains things

Cleaning & Lubrication

  • AGI cleaning & lubrication methods shown, along with the reasons for their use
  • After cleaning, dry with air gun, or in the oven on Warm ~185-200 degrees (metal parts ONLY)
  • Lubing the Bob way, and what kind he likes

Reassembly & Troubleshooting

  • Forend, barrel and magazine reassembly
  • Bolt reassembly
  • Extractor rules and adjustments if necessary
  • Bumping pins and screws to be sure it does not disassemble itself
  • Trigger group reassembly
  • Troubleshooting; Chamber bushing and how it is blend reamed, but youre going to have to have a competent gunsmith with the special reamer set do it for you
  • Troubleshooting; headspace how to correct it the right way
  • Troubleshooting; misfires from firing pin strikes to the right, two ways to correct it
  • Receiver reassembly
  • Safety testing


  • General overview
  • Inspecting a model 12 for possible purchase

If you noticed how often the terms "explanation" and "demonstration" are used, you may be getting some idea of why this course is necessary for any Winchester model 12 owner, or someone who intends to be.

How much does your Professional Course cost? The answer can be found in our intro pack. We recommend to anyone considering our Professional Course that they get the Introduction to Gunsmithing Packet as this packet includes a video with a sample gunsmithing lesson. It also includes an Enrollment Form that lists the costs of each Course level available as well as the material covered in each level.

Do I have to pay $7 s/h on each retail video? No, we discount shipping on multiple video orders. The new website calculates shipping based on weight and destination. In most cases, the actual shipping is less than listed in the catalog.

Is there a time limit to complete your course? No, our course is self-paced. As you complete sections of the course and submit your tests, we provide certification of completion for that portion of the course.

Can I become certified by taking your retail courses? Answers vary. If you are intending to purchase all the videos in our Law Enforcement Armorer's Course, for example, as long as you buy the test separately you can obtain a Certification as a Law Enforcement Armorer once you complete the testing successfully. Otherwise you would need to purchase one of our certified professional courses in order to obtain a profession Gunsmithing certificate.

What does your Professional Gunsmithing Course Introductory Lesson cover?The Introductory Lesson is one hour and includes complete information on how to get started Gunsmithing. You will also learn how to insure reliable auto-pistol feeding and how to prevent jams, checking and adjusting "range" on Smith and Wesson revolvers, how a gas system works on a Colt AR-15, AR-7 trigger repairs, timing and understanding cartridge stops of a Remington 870 and much more! 

Are your Courses guaranteed? Yes! The American Gunsmithing Institute is proud to offer a 100%, "Bulletproof Guarantee." We are so sure of the quality of our Courses and products that you may return any item purchased directly from AGI for a full refund (less shipping) for up to 90 days after purchase date. Defective DVDs and videos will be replaced for up to 1 year. The only question we will ask is: "How did we fail you?"

Does AGI offer other Certified Courses aside from the Professional Gunsmithing Course? Yes. We also offer a Certified Machine Shop Course, complete with Lathe, Mill and general Machine Shop instruction. Additionally AGI offers a Certified Welding Course and a Certified Locksmithing Course.

What do the Disassembly/Reassembly Courses cover? AGI offers D/R Courses that clearly demonstrate the complete process of disassembly and reassembly step-by-step. The Courses use close-up views to provide comprehensive instruction. Each DVD Video Manual covers one specific model or family of firearms and is indexed to help the user quickly find the information that they are looking for. At the price of only $19.97 each (plus s/h), these video manuals are must have support information for anyone who owns one of these firearms.  

What do the Armorer's Courses cover?AGI's Armorer's Courses teach you how to disassemble, maintain, repair and reassemble your choice of the 51 guns featured. These videos are packed with exclusive information and are equal to a complete Factory Armorer's Course! While our Disassembly/Reassembly Courses contain invaluable information, our Armorer's Courses contain so much more. Master Gunsmith and AGI Instructor Robert "Bob" Dunlap explains design and function using exclusive factory cutaway firearm models, giving you close-up details of the internal functions you would not otherwise be able to see. All AGI Armorer's Course DVDs include a FREE printable schematic!    

Are your Instructors experienced in their fields? Absolutely. Master Gunsmith and AGI Senior Instructor Robert "Bob" Dunlap is a widely respected authority in the firearm industry and spent over 35 years as the senior instructor at Lassen College's internationally known Gunsmithing School. Master Gunsmith Gene Shuey is a world class custom gun builder, former world class competitive shooter and current trainer specializing in 1911 and Glock pistols, IPSC limited and open class guns, and high-end custom rifles. Darrell Holland is a well known custom rifle builder, writer and lecturer who is always inventing new performance shooting products. Ken Brooks is a graduate of the renowned Gunsmithing program at Lassen College and continues his journey by working full time for Bob Dunlap. Gene Kelly is the President of AGI and the Gun Club of America. He graduated from Lassen College's Gunsmithing program and worked as a Professional Gunsmith prior to founding AGI. T.R. Graham is a NRA Certified Pistol Instructor and is a known authority, author and Gunsmith specializing in Glocks and other handguns. Master Armorer John Bush is an AGI Instructor and a consultant to manufacturers and importers of military firearms, and is certified as an Expert Witness in firearm cases.