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.

Weight0.25 lbs
Dimensions7.56 × 5.44 × 0.63 in


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