Winchester Model 12 Disassembly/Reassembly Pictorial Guide
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Author:  nody [ Fri Feb 28, 2014 11:25 pm ]
Post subject:  Winchester Model 12 Disassembly/Reassembly Pictorial Guide

Welcome to Winchester Model 12 ownership and care! {hs#

If you are just thinking about getting one, and you will be in the vicinity of St Louis, you can rent one of dozens of beautiful M12's and Super X One's here at the Winchester company-owned club:

It is located in East Alton, IL, right across the Mississippi River, and right up the road a mile from the Olin Winchester ammo plant, where all their shot shell manufacturing still takes place:

After a long delay with no free time to correct the damage Photobucketup did to my OP, I've made some time to do a complete rewrite, using to host the pics, hopefully forever. Everything is brand new, except the gun itself! :mrgreen:

M12's are still plentiful and fairly inexpensive these days, with over 2 million manufactured between 1912-1963, and a few after that. Unfortunately, despite that they were pricy in their day, they too often have been left dirty, and many are rust buckets, mine included, thanks to unknown previous owners. It still shoots like a dream, though! 8)

The rust may be because taking them apart to clean them properly is an intimidating mystery to some owners, though as you will see, it shouldn't be. :?

All references are from the butt of the gun, looking forward towards the muzzle, and part numbers and names used, as this diagram shows:


The M12 shown in the assembled and ready to fire condition:

LOCKING AND UNLOCKING THE MAGAZINE -- Separating the gun into two halves, known as "takedown."

The first step of disassembly, (and last step of reassembly in reverse order,) is to unlock (lock) the Magazine tube (21) ("Mag" hereafter) for takedown. This can be done as often as you like, and becomes second nature with practice, just like an O/U. I keep my M12 in a takedown case, just like my O/U.

The Magazine locking pin (19) ("Mag pin") is shown in the locked, ready to fire, 11 o'clock position:
Note the Mag is fully rearward, (locked and ready to fire condition,) with the Mag pin right next to the Magazine band (14) ("Mag band").

During takedown and reassembly, you must take care for the threads on the Barrel (11) and Mag, and their mates inside the Receiver (1):

Depress the Mag pin to the 5 o'clock position, then rotate the Mag pin and Mag together (the pin is your lever) to the 8 o'clock position, one-quarter turn:

If the Mag won't turn with the leverage provided by the Mag pin and your fingers, you may have grime, rust, or damage, either under the Mag band, or in the Receiver/Mag threads.

IF AND ONLY IF it won't turn easily, first try removing the Magazine band bushing screws (12) ("Mag band screws") (shown installed above/removed below) to allow the band to be spread a little bit wider on the Mag:

The Mag band should never make immovable contact with the Mag, but it does hold the Barrel tight when the two screws are installed, by design. The Barrel is fixed, the Mag is designed to slide forward and rearward through the (snug) Mag band, only when unlocked, to disengage the receiver for takedown.

The Barrel above is shown popped out (the Mag band functioning like a "U-shaped" spring with the screws removed.) This is the normal way the Barrel is ***LATER STEP*** separated (and reinstalled ) from (to) the Mag.

Also, the "Barrel flange" is shown, which goes into the Mag band and Magazine band bushing, (13) into mortises cut into them.

***As with everything on neglected guns, if something is stuck, soak overnight or longer with penetrating oil. If that doesn't free it up, see a gunsmith. Never use tools which generate excessive leverage. This gun is designed to only need a 3/16th" hollow ground standard tip screwdriver to disassemble.***

Assuming the Mag slides freely, slide the Mag, Action slide (25) and Action slide handle (28) ("Slide") forward about 4" until they all contact the "Mag flange:"
The Mag flange's rear edge is the forward limit of travel for the Action slide sleeve screw cap (27).

The Slide, cap, and handle are normally left installed on the Mag. The cap requires a special tool from Brownell's, or a home made one, to remove, and there is no reason to for normal cleaning.

The Action slide (25) bar must be fully retracted from the Receiver, BEFORE you attempt to remove the forward half of the gun from the rear half.


***THIS IS PROPER:*** Action Slide bar fully flush with the Receiver extension (8) BEFORE you try to separate the halves:

Hold the Buttstock (47) and Receiver still, keep forward pressure on the Slide, and rotate the forward half of the gun just slightly less than one-quarter turn clockwise, then gently draw it forward and clear of the Receiver, carefully so as not to bung the threads. A good "cheat" is to hold the gun vertically, so there is no side-load on the threads.

The M12 in takedown:
Note again, the difference between when the Mag is unlocked, above, slid about 4" forward from the Mag band, compared to when it is locked:

SEPARATING THE BARREL FROM THE MAG -- It's going to start getting tricky now!

The Mag can be left internally intact or disassembled, on or off of the Barrel, your choice. The exception is if you want to remove the Mag band and Action slide handle retaining (leaf) spring (15) from the Mag. To remove those, both the Barrel/Mag separation and Mag disassembly are required, together, but we'll hold off on that, until we disassemble the Mag.

Once the forward half of the gun is free of the Receiver, set the Receiver aside.

As mentioned above in the stuck Mag band comments, remove the Mag band screws, and "pop" the Barrel apart from the Mag by inserting the fingers of both hands in the gaps between the two parts .

The Barrel and attached Receiver Extension is then set aside for normal cleaning. Leave the Extension attached to the Barrel. Removing and adjusting Barrel tension is only for a well-experienced M12 gunsmith to attempt.

Reassembly will again be the reverse:

Gently place the rear end of the Mag into the Receiver extension

Line up the Barrel flange with the reassembled and installed Mag band and Magazine plug stop (16), (see below, looks like Felix the cat)

Make sure the Mag flange (not the Barrel flange) is at the 9 o'clock position:
Squeeze the Barrel back into the Mag band, by making "fists" around the Barrel and Mag, and slowly closing them.

Finally, reinsert and tighten the Mag band screws. Some may wish to consider Blue Loctite?

This too all becomes second nature with practice, though it need not be done regularly, unless the gun gets wet or you want to "deep clean" it.

DISASSEMBLY AND REASSEMBLY OF THE MAG -- Now it starts getting a little complicated! :?

The Mag pin has a small "spring-clip" set into a slot on the side of the pin. One end of the spring is rounded, the other forms a protruding "tip."
Note above, the spring inside the Mag pin has been depressed with a small standard screw driver (the only tool required) and removed from the Mag, then partially reinserted to show the proper way it is reinstalled, later. It only works one way!

***The rounded end of the spring MUST BE reinstalled on the 8 o'clock end, and the protruding "tip" towards the 2 o'clock end. Memory aid: "TIP-TWO" (like "tip-toe")***

Next, reverse the Mag pin and stick it back in its hole as an easily removed "keeper," while you remove the two tiny Magazine plug screws (18) (also shown are the Mag band screws)

***If you don't do it this way, if the pin is completely removed and you unscrew the plug screws, the Magazine spring (22) will shoot the Magazine plug (17) (not the Three-shell wooden plug (24)) out like a rifled slug of just about exactly the gauge your gun is!***

Conversely, if you leave the Mag pin installed normally, and first remove the plug screws, you will have nowhere near enough hands to hold the gun, and the plug, and try to work the pin spring out of the me on this!

Then the Mag plug is held by the thumb against spring pressure, the Pin easily withdrawn, set aside, and then the Spring tension slowly released, covered with the palm of the free hand.

Remove the Mag spring and Magazine follower (23) and clean, swab with oil, and/or replace with a new spring to your heart's content.

My gun was built in 1929, and while I have no idea if this is the original spring, my gun never got a drop of love before I bought it about 5 years ago, and I haven't replaced it. Seems to work perfectly, and I shoot a fair amount of trap, skeet, 5-Stand, and Sporting Clays with it, far more than its previous lifetime total round count, judging by the lack of internal wear. :D

Next is removing the above mentioned Magazine plug stop (16), "Felix the cat." It is a ring with two "ears," one for each side of the Barrel. It slides off and on the rear of the Mag plug, obviously. The trick is remembering which way it goes back on!

Finally, now you can slide off the Mag Band, its Magazine band bushing (13), and the Action slide handle retaining spring (15) (leaf-type).

That is the Mag totally disassembled, if ever you want/need to do it.

Removing parts on the M12 is easy, but there are several WRONG ways to reinstall them, and only one correct way!

First, back on with the Mag band, AFTER you correctly install its bushing; that means the large-side cutouts with threads showing are upwards, towards the Barrel.

Next, slip the leaf spring back under the band:

Now it's time to rebuild the Mag internals:

First, put the Mag follower on the Mag spring, and loosely insert in the Mag.

Next, the slot in the Mag plug goes on the opposite (right) side of the mag flange. This slot and the gauge-stamped tab on the Mag plug stop (“Felix”) is what limits the rotating of the Mag to one-quarter turn.

Before inserting the Mag plug in the Mag, the plug stop is slid over the rear of the plug, with the stamped gauge number on the tab facing towards the rear of the Mag (follower end) and the tab in the slot.

Then, compressing the Mag spring flush with your fingers, the Mag plug is inserted in the Mag, with the plug stop ears pointing up to receive the Barrel.

It is all temporarily held together with the reversed Mag pin again, then the plug screws are replaced and tightened. Some may wish to consider Blue Loctite?

Finally, with the plug screws tight, the Mag pin is withdrawn, and reinserted properly, FROM the 8 o'clock direction, with the "tip-two" (o'clock.) The pin spring is depressed with the screw driver tip, and the pin inserted.

It now will not fall out (the purpose of the tip,) but it also will cycle from unlocked to locked properly; if it is installed incorrectly, it won’t cycle properly, or it may fall out on the ground and could be lost.

The Mag pin is left in the 8 o’clock position until you wish to rejoin the two halves of the gun.

RECEIVER COMPONENTS -- Only four parts to worry about, and they are almost all easy!

The trigger/carrier group is called Guard-complete assembly (45). I advise leaving it together as a unit. Yup, call the gunsmith if it needs more than a spray or dunk job. The screw heads are staked, if that gives you an idea of their permanency:

Removed the one screw at the rear end of the trigger guard with the aforementioned 3/16ths" hollow ground standard screwdriver.

Pull down and rearward on the Trigger Guard. A slight side-to-side wiggling may help. If jammed, soak overnight with penetrating oil. If still jammed, yup, see a gunsmith.

Cartridge cutoff (29), and bottom of Breech Bolt (31):
Shake the gun, and the cutoff should fall out. If wedged in with grime, gently press ends with fingers to rock back and forth. As a last resort pry very gently after soaking in penetrating oil overnight; it is only held in by shallow round mortise in the center. Or, back to the gunsmith if it has REALLY been neglected! :roll:

Next, lay the receiver on its left side, with Ejection Port facing up. Remove the Ejector and ejector spring (30), by gently prying with your screwdriver:

Next, remove the Breech bolt. Memory aid: "rocker switch," shown depressed forward for shooting forward.

Depressed reward for removing bolt rearward from receiver:

The receiver is now empty.

Reinstall in the reverse order:

Hold Receiver upside down, and slide Breech Bolt "up and in," held flush against top of the receiver with your finger, against the Firing pin retractor (35) spring pressure

Breech bolt rocker switch depressed forward with you screw driver. ("forward to shoot forward.") You can now take your finger off the underside of the bolt.

Lay the Receiver of its left side, ejection port facing up.

Slide in the Ejector spring in flush, using just your fingertips. Start behind the slot, and gently guide it forward; it will drop right in! If it gets stuck sideways, remove with screw driver and try again; it becomes easy with practice, just like everything else.

Lay the Cartridge cutoff back into its slot and round hole

Guide the Guard back in and up, careful not to knock out the cutoff, and reinstall the screw at the rear of the trigger guard.


To reassemble the two halves, make sure the Mag pin is in the 8 o'clock position.

With the forward half of the gun turned slightly less than one quarter clockwise to the rear half, so the Barrel threads mesh with the Receiver (lack of) threads, gently slide them together, making sure the Slide is fully forward, which holds the Mag and slide bar fully forward.

Rotate the forward half counter clockwise, again assuring the slide bar is fully retracted. Align the Mag with the Receiver. Slide the Mag aft until its threads are aligned, then lock with the Mag pin by rotating the Mag from 8 o'clock to 5 o'clock. Then pushing the fin through to 11 o'clock position, which keeps the Mag from unscrewing.

The gun is now ready to shoot! {hs#

Author:  SuperXOne [ Mon Mar 03, 2014 12:13 am ]
Post subject:  Re: Winchester Model 12 Disassembly/Reassembly Pictorial Gui

This is the very best thing I've ever seen for a Model 12 owner to be able to take down his gun and keep it clean and lubricated. It also shows why I keep on preaching that when you buy a Model 12 you want a good functioning Model 12 to begin with. For not a lot of money, you can have a Model 12 re blued and the wood finish refreshed so it looks really good. But it takes an experienced gunsmith and a good pile of money to work on the internals of a Model 12.

The Model 12 just oozes quality and class and hand fitting. Every shotgun gun addict should have at least one or two in every gauge.

Thanks, nody, for posting this again. It will do a lot of Model 12 owners a world of good.

Author:  RockedEm [ Sat May 31, 2014 7:04 am ]
Post subject:  Re: Winchester Model 12 Disassembly/Reassembly Pictorial Gui

The one thing that could stand to be added and I found a link somewhere is a pictoral guide to removing and installing the left and right hand side extractors. You can find them if you search around. The way the Model 12 extracts and ejects a worn extractor on either side can cause much grief.

The "right side" or port side extractor is easy enough in that you simply depress the plunger with a flat screw driver and lift out the extractor then the plunger and spring fall out.

The "left side" extractor is trickier, but accomplishable with some care. Make sure the "rocker" that is the bolt lock is pushed such that the end closer to the bolt face is "out" away from the bolt. Drift out the pins that goes up through the top of the bolt. Remove the extractor and pins and replace.

Wish I had pics, but I have done it for a couple times and I can't impress enough that if you are struggling with extraction and ejection issues to take a look at replacement of the extractors and ejector due to wear.

These can be accomplished at home for about $100 in parts from Nuline and an hour of your time. ... 42&alpha=E

I used the left and right side kits and they fit PERFECTLY; dropped in my 1941 M12-16ga and the kit was marked for use with 12, 16, 20.


Author:  nody [ Mon Jun 02, 2014 7:30 pm ]
Post subject:  Re: Winchester Model 12 Disassembly/Reassembly Pictorial Gui


I thought about going into that, but I had to draw a line, so I drew it at anything that was staked in place, as are the BREECH BOLT pins.

As I said, going further than what I wrote above is only for those with a very detailed manual, a vise, proper punches, and at least a decent amount of amateur gunsmithing ability.

Author:  RockedEm [ Wed Jun 04, 2014 7:35 am ]
Post subject:  Re: Winchester Model 12 Disassembly/Reassembly Pictorial Gui


I didn't say it, but thanks for everything you put together. It is awesome and yes (as you know) the Model 12 is a beauty, but could and has have many many detailed books published on maintaining it.

Hopefully the few things I wrote about the ejector/extractors help in a little way for someone that is looking for a little guidance there since they are a couple of the top wear items that can cause much frustration to the users of these fine shotguns.


Author:  forehire [ Thu Feb 12, 2015 10:44 pm ]
Post subject:  Re: Winchester Model 12 Disassembly/Reassembly Pictorial Gui

I read your post, printed it, and then had it hard-book bound. Best info. on a Model 12 I have seen. THANKS

I have just received a New-in-the-box 1972 Y trap.

Carry On

Author:  DallasCMT [ Fri Feb 13, 2015 12:27 am ]
Post subject:  Re: Winchester Model 12 Disassembly/Reassembly Pictorial Gui

I am just now seeing this post, due to the post above making the thread recent.

This is a fantastic post and I really appreciate it. Wish I had seen it last year! I have a 4 digit S/N 20 ga from 1912, it was my dad's, dad's gun, and I cherish it.

Author:  nody [ Sat Feb 14, 2015 12:29 am ]
Post subject:  Re: Winchester Model 12 Disassembly/Reassembly Pictorial Gui


Author:  DallasCMT [ Sun Feb 22, 2015 1:34 am ]
Post subject:  Re: Winchester Model 12 Disassembly/Reassembly Pictorial Gui

Maybe I should open my choke, too. It's stamped "Full" but I'd prefer it to be IC as well. It is a first year gun S/N 14xx and of course a 20 ga. I had to get the chamber lengthened to 2-3/4", but left the choke alone at that point. I rarely shoot it, but should get it out more often. I think of it as old (103 years! ) and fragile but it can probably go another 100.

Author:  nody [ Sun Feb 22, 2015 8:25 am ]
Post subject:  Re: Winchester Model 12 Disassembly/Reassembly Pictorial Gui

Yeah, at first I agonized about "destroying" 80+ years of "history" on my 1929 M12 by having the choke opened, sort of like doing plastic surgery on grandpa. It occurred to me though that 80 years was mostly spent sitting unused in a closet without enough rust preventative on it; hardly a history worth keeping.

Those old FULL chokes were super-full because of the card wads and probably also because shotguns back then meant shooting waterfowl for dinner, with long pass shots. Nobody shot a dove with a 12 gauge back then probably, as they would see it as a waste of lead and probably unsportsmanlike. If they shot any clays, it was American Trap.

The FULL guns are just not much use anymore with plastic shot-cup wads. Given how badly "modified" the majority of M12s I see are, modified by rust, or poly chokes/Cutts, having the plain barreled choke opened to something useful like IC or LM really isn't damage. You will see NO alteration to the gun except some faint crosshatched burnishing of the inside of the muzzle, which actually looks nice.

These guns were made to shoot and be cleaned, and shot again; IOW, enjoyed. They've already spent enough time in the closet.

Here's the link to Mike Orlen's price sheet and address. He's done two guns for me, and the results are fast, economical, and PERFECT; this M12 patterns beautifully, and the 1100 he threaded for me threads like the bezel on a Rolex. EVERYONE here has had great results with Mike.


As far as working with him, if you have not already, I recommend NOT calling ahead, as he stays busy working and is not running a "help line." Just ship the barrel only, with a note telling him what you want, and a personal check or MO for the amount plus return shipping as listed on the price sheet. You don't need to deal with any FFL nonsense for repair to your own gun, and you are just sending the barrel anyway, not an operating firearm. You should have it back in 2-3 weeks at the most.

You will shoot your M12 a lot more after this is done! {hs#

Author:  DallasCMT [ Sun Feb 22, 2015 12:42 pm ]
Post subject:  Re: Winchester Model 12 Disassembly/Reassembly Pictorial Gui

Thanks for the info. It looks like a choke tube installation is not that much more in cost, except for the costs of the tubes, of course. That would alter the originality of the gun more, but would make it more universal. I cannot see putting an extended choke tube on an old classic!

Author:  nody [ Sun Feb 22, 2015 6:43 pm ]
Post subject:  Winchester Model 12 Disassembly/Reassembly Pictorial Guide

Early production M12 barrel is in all likelihood too thin to thread.

Fixed chokes seem like a car with only one gear, but they are really sweet; no worrying about which choke to use, easy to clean, retains the original look of the gun. Hard to beat IC for universality, and I shoot SC with LM/M in my CG Ascent.

Author:  bill4282 [ Mon Mar 16, 2015 5:14 pm ]
Post subject:  Re: Winchester Model 12 Disassembly/Reassembly Pictorial Gui

need help. A friend handed me his grandfather's model 12 and asked me to look at it and see what I thought it was worth. After researching, so far,I found this thread and thought someone on here might give me an idea. Based on the serial number, it is pre-1966 which is good news. Bad news, it was a 20" riot gun with Cutts. Someone along the way hacksawed off the Cutts and welded on a piece of barrel to make it 28" leaving a bulge in the barrel at the point of weld. The buttstock wrist is cracked on both sides. Bluing about 80%. I haven't fired it so don't know about the mechanics. Any ideas?

Author:  nody [ Thu Mar 19, 2015 10:50 am ]
Post subject:  Winchester Model 12 Disassembly/Reassembly Pictorial Guide

Given the barrel mauling, cracked stock, and poor bluing, I'd guess you are talking < $200.

Your best bet here would be to start a new thread in the Winchester forum with pictures.

You can also go on and do a search on Winchester Model 12, and look for comparable guns.

This thread is about M12 maintenance, not resale values.

Author:  Rastoff [ Fri Mar 20, 2015 12:18 pm ]
Post subject:  Re: Winchester Model 12 Disassembly/Reassembly Pictorial Gui

I thought this video would be a good addition to this topic:

Author:  DallasCMT [ Fri Mar 20, 2015 10:17 pm ]
Post subject:  Re: Winchester Model 12 Disassembly/Reassembly Pictorial Gui

That's slick!

He always makes things look so easy... :-)

Author:  Ridge Runner [ Sat Apr 18, 2015 8:10 pm ]
Post subject:  Re: Winchester Model 12 Disassembly/Reassembly Pictorial Gui

Thank you for creating this post! I just bought my first Model 12 and will be printing this off for future reference.

Again, Thank you for doing this!!!!

Author:  Col. Colt [ Sat May 30, 2015 3:00 pm ]
Post subject:  Re: Winchester Model 12 Disassembly/Reassembly Pictorial Gui

I wish to also extend my heartfelt thanks for all the time and preperation in making this takedown guide for the rest of us!

At just over 60 years of age, I finally got a Model 12! Mine was a pawn shop "rescue", cheap because of a Polychoke and fingerprint rust on the reciever - otherwise mirror bright bore, 1948 production, good wood with White Line recoil pad. I've been reluctant to take the magazine tube off, now, thanks to your fine guide, I will do that.

I had no idea how magnificent a Model 12 is! Machined perfection! So far I've bought an original Winchester plug (after finding an amazing machined aluminum plug, hand turned, in the gun!) and a $50.00 book! I may need another Model 12 soon! CC

Author:  hardhar55 [ Sun Dec 13, 2015 11:27 am ]
Post subject:  Re: Winchester Model 12 Disassembly/Reassembly Pictorial Gui

Can anyone verify the necessity for the "action slide handle retaining spring" No.15 in the parts diagram.
I see numerous pics & vids with it missing.

Author:  nody [ Thu Jan 07, 2016 11:54 pm ]
Post subject:  Re: Winchester Model 12 Disassembly/Reassembly Pictorial Gui

Mine was missing during that period. The gun worked fine.

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