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75172 Views 32 Replies 2 Participants Last post by  gearchecker
To determine the correct sight height to correct an elevation problem, multiply the sight radius, in decimals by the elevation error and then divide the results by the distance to the target, in inches.

Sight radius 5 3/4" = 5.75
Shooting 5 inches low
Distance to target 25 feet or 300 inches

5.75 X 5 divided 300 = .09583

The front sight would have to be lowered .096 inch or the rear sight raised that amount (or a combination there of) to raise the point of impact.

Sight radius 4" = 4
Shooting 6 inches low
Distance to target 25 yards or 900 inches

4 X 6 divided 900 = .0266

The front sight would have to be lowered .027 inch or the rear sight raised that amount (or a combination there of) to raise the point of impact.
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Internal Lock
Lots of curiosity on this subject so I'll leave a few pictures for members that would like to see what it looks like.

The first thing you do is remove the stocks and slide plate. When you lift the hammer off it's stud, you will see this cam or what some call the flag. The flag is the part on your gun which goes up or down to lock or unlock your revolver.

As you turn your key, this twisting motion is the force which lifts the flag to lock your gun.
Attached to the flag is a tiny wire spring. The other end of that spring is placed into a small notch in the frame. The spring is not pictured in these pictures. It's located on the back side of this view. This tiny spring is the power behind your flag dropping down, "unlocked."

The way they assemble it at the factory, the lock goes in first, then the bolt and so on. The bolt is that black bar in the picture. The cam (painted red) basically rides inside the hammer. It's a very simple lock.

My only intention is to educate members about the IL mechanism.

Because of legal ramifications, I'm not recommending the IL be removed or modified.
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Production numbers for S&W and other makes

Not counting 2006 or 2007 (figures not posted yet), 2000 thru 2005 S&W sold 768,736 revolvers

new link below...
Range rod to check barrel/cylinder alignment

In case anyone would like to know how to inspect their revolvers using these inspection tools, here are the instructions:

The use of a standard service diameter insert gauge also called a plug gauge and/or range rod to check barrel/cylinder alignment. Do this test automatically as a part of checkout on all accuracy problems, lead spitting complaints, and as a part of accurizing and tuning work. This is the basic test for misalignment of cylinder to barrel (or reverse). The usual small, built in variations in manufacturing variations in revolvers are compensated for the funneling affect of the forcing cone. Additional clearance undersizing of the gauge insert makes passing this test easy for the majority of production revolvers. A match diameter gauge (available in .38 caliber only) is also available.

Make this test with the barrel pointed straight up. This allows the insert to automatically find center. To test alignment, cock the hammer back into firing position at each cylinder (on newer revolvers hold trigger down to the rear) and then slide the insert down through the barrel and cylinder junction while feeling for entry and travel resistance. With a correctly aligned yoke, straight ejector rod, center pin and a clean barrel, all revolvers should allow a standard service gauge insert to pass thru without resistance or drag. If entry into the cylinder is resistive in all or most chambers, and yet cylinder alignment checks, block the cylinder stop and retest with the cylinder block unlocked. If the results are the same, something is tweaked. The frame is the likely candidate. But if only one or two chambers show resistance, then there is a possibly of deformity or abnormality at the cylinder locking slot or at the ratchet.

Use the larger 38 cal “match” gauge insert for the closer tolerances required in match or competition work. Standard 38 service gauge inserts measure in at nominal diameter of .345” while the match gauge runs around .3455”. When working with the larger diameter custom bull barrels designed for hollow base wad-cutters, you should use a slightly larger insert such as .350” or .3505” for precision work.

It is a bit foolish in my opinion to consider using match diameter gauge insert in a production barrel, with the serious expectation that it will gauge at this diameter. Although, I have found that some production barrels will, particularly earlier K-38 revolvers.

My personal range rods measure at the following:
22 LR .2179”
38/357 .3446” (standard rod)
44 cal .4157”
45 Cal .4417”
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Polishing stainless

What I found to clean and polish my stainless guns is gray (medium) and finish up with white (very fine) scotch brite pads with a little gun oil to help move the metal. Brush the pads to the original "grain" and you won't need to use any polish at all. The guns will look much better than original. REMEMBER tape over any laser engravings or you will rub them away very easily.

When working with Scotch brite pads always start with the finer grades to test the finishes applied.

Don't use steel wool. it's messy and you run the risk of rubbing carbon into the surface which might rust the finish.

If you don't want the brushed look, Mothers Mag polish is recommended by myself and others here on this forum. This polish applied will make your revolver's finish look like a professional machine buffed job in short order. I tried many polishing compounds and even tried lapping compound on the finish but Mothers is amazing stuff. Again, don't rub the laser markings!

The glass beaded surfaces can be polished off so use care around top straps as well.

Blue guns are not fixable and need to be sent back for a re-blue. Cold blue (over the counter products) will not match the S&W blue finish.
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Gun stocks or grips

S&W tends to call them stocks. Most everyone else calls them grips. On early models, the guns serial number is placed inside the right grip panel.

The best way to remove grips is to unscrew the screw a few turns and tap the head of the screw with the screwdriver handle to push the right grip panel off the frame. Prying the grips with a screwdriver should be avoided.

Fancy grips of pearl, ivory, stag exotic wood, or other wood were available from S&W as well as aftermarket suppliers. Around 1893 factory grips had the S&W medallions inlaid into the grips, while aftermarket grips were plain with no medallions. Pearl and ivory grips may be found with checkering or relief carvings.

Tip-up revolvers all carried smooth rosewood stocks.

Top-break revolvers such as Schofield’s, Russians and the American carried standard smooth walnut grips.

Hard rubber grips came into the seen around the late 1870s. Checkered wooden stocks were very common on the new model #3. The nickel baby Russian’s was made with hard rubber grips, while the blue Russians were given wood stocks. Most hard rubber grips had the logo at the top of the grip. There was a red rubber variation, which was only found on the revolving rifle. I have read that blue grips were reported seen on them as well.

Early Hand Ejectors
Grips were hard rubber in the beginning but were soon replaced with walnut. The large N frames began in walnut in 1907. Gold inlaid medallions made into walnut from 1910-1917. From 1917-1929 standard walnut grips had no medallions. From 1929 chrome or silver medallions were introduced.

Magna (service grip) grips were now offered as an option on the .357 in 1935. Magna grips are made higher on the blackstrap, while leaving the front and rear strap of the frame exposed. These grips became the common style. In later years, they were considered the service grip.

Grip adapters are metallic or rubber pieces that fit on the front strap of the grip frame. S&W as well as others made them. They were found on police revolvers mostly until Pachmayrs came into being.

The diamond grips have a diamond of uncheckered wood around the grip screw and escutcheon. They were introduced as early as the 1880s and were standard into the 1960s.

Coke bottle grips are diamond grips made in the 1950s and 1960s, which have a girlish or coke bottle appearance to them.

Modern revolvers.
Exotic woods such as Birdseye maple (1950s) or Rosewood until about 1978. Goncalo Alves from South America, replaced walnut around 1975 to become the standard for oversized target grips. These grips are standard on large framed revolvers. Large target grips were also offered in smooth (no checkering). Speedloader cutouts were common in the 1980s.
Combat grips (with finger grooves) are common in both square and round butt conversions.

Today, S&W no longer makes grips and it’s common to find rubber grips on all standard revolvers. The massive X frame, 460 and 500 Magnum revolvers uses the L frame round butt grip. Today round butt frames are our only option, so grips are found in a round butt or conversion grip style that simulates the old square butt feel, made in wood or rubber.

500 rubber (X frame conversion grip), smooth combat (notice the speed loader cutouts), target, J frame service (or Magna) and smooth target grips new in package
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Barrel Length / Muzzle Velocity

A little over 20 years ago the American Rifleman staff did a test using a 44 Magnum revolver equipped with a 18" barrel that was shortened in one inch increments. Five shots were fired at each barrel length, with each of the three brands of factory loads, Federal, Winchester and Remington, all using 240 gn bullets. The instrumental velocities shown are the averages obtained, after smoothing the data to remove the effects of random variations in velocity and thus to represent the incremental velocity changes more accurately.

1" 742 FPS
2" 935
3" 1067
4" 1165
5" 1239
6" 1298
7" 1345
8" 1384
9" 1417
10" 1445
11" 1469
12" 1490
13" 1508
14" 1525
15" 1539
16" 1552
17" 1564
18" 1575
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Side plate removed

Here is a picture of a 686-3 L frame 357 mag under the hood. It gives the user an idea of what the action looks like. The hammer block has been removed for the picture.

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Removing Rear Blade

To swap the rear blade:

When changing the rear blade on S&W revolvers, turn the windage screw clockwise until the screw breaks. Then remove the nut by unscrewing if from the base. Use a plastic bag to catch the tiny spring and plunger that is located inside the screw head.

Reinstall the parts and tighten the retaining nut fully then back it off ¼ turn. Use the stacking tool and crimp the nut. Job done!

Tools look like this:

Rebuild kit looks like this:

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Check Sing

In a panic situation, the hand could skip by a ratchet, and the gun won’t fire.

Press trigger back enough to clear the cylinder stop, then spin cylinder. Listen for the hand clicking on the ratchets.

Press back and left = Left sing
Press back and right = Right sing
Press back straight = Neutral sing

If your right handed you normally pull the trigger to the right.

If no right sing: Bend hand over to right side of the window. To do this simply insert screwdriver underneath the hand and lift upward.

If no left sing: You will have to remove hand and tap it with a hammer to bend the hand over to the left side of the window.

The third way it could be out, where you can’t correct the right or left sing, the hand is twisted.

Ideally, you want the gun to sing no matter how the trigger is pulled. New guns may not be adjusted proper, either. Check yours for fun...
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500 Magnum custom compensator

S&W doesn’t sell a break with no holes for the 500, (like the 460 Magnum) so I modified a 460 into a 500.

This is how I did it:

Face the back of the compensator off .02 with a lathe. Maintain the shoulder outside step at .04 and the over all length of .905 long.

Bore the inside first shoulder step back .02. The inside diameter is .805 so don’t over cut this dimension as it aligns up on the front of the barrel.

Then bore the hole thru at least to .531 so that big slug can find it’s way out. I made mine a little bigger at .550 inch.

It locks up snug in my revolver and it looks factory but it’s not!

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Feeler gauge inspection

Here are the general specs for basic checking on S&W revolvers.

Whenever I check the specs of S&W revolvers there are 3 things that I check, air gap, head space and endshake.

In a nut shell here is how I do it.

Proper air gap on S&W revolvers is .004-.010 inch. Rotate the cylinder and check it in more than one spot. The cylinder won't be perfectly square, it will vary some. Measure it at the forcing cone. Too little gap the gun will jam, too much and the gun will start spitting, plus lower bullet velocity and accelerated top strap erosion.

Set end shake for less than .002". Here is how I test it. Push the cylinder forward, check it. Pull the cylinder back, check it again. The difference is endshake. Measure it at the forcing cone.
If I need to adjust it, I use end shake bearings, instead of peening or flaring the yoke's barrel. A gun needs some endshake to run, too little and it will jam, too much creates all kinds of problems, possible light hammer strikes, poor carry up etc.

Head space:
Here's how I test it: With new or once fired cases in all chambers (no primers). Wedge the cylinder back by placing a shim between the barrel and cylinder face (a gap gauge works well. This forces the cylinder back where the extractor's hub is bottomed out on the recoil shield. You should have .008-.012" (.010" optimum) gap between the case heads and the firing pin hole on the frame.

Keep in mind the ejector and cylinder are made and fit at the factory to work together for proper head space. Swapping parts may throw off the head spacing.

Normally, head space doesn't change unless someone files down the hub of the ejector.

I added the gage specifications below for each particular caliber (from the armorer's manual):

38,357,41,44 .060"-.068"
22 magnum .004"-.008"
45 ACP .090"-.094"
45 Long Colt .060"-.068"

38,357 w/cylinder Counter Bore .012"-.018"

In addition no revolver should be adjusted to a single action trigger pull of less than 3 LBS.
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What is MIM?

Here is an older post that I have copied here, what is MIM?

By popular request, here's the post from Mr. Herb Belin of S&W -----------------------
"I have read with much interest the many comments in this forum pertaining to MIM, MIM Parts and the use of same in a S&W product. So far I have come away with several impressions and they are "people in general don't like/trust MIM parts" and "no one has said why" I will take a stab at this issue and see where it goes.

As background to our decision to use MIM in some areas of our Mfg Process we took a long hard look at our "Life Time Service
Policy". It was clear to us that any change in any of our products such as the use of MIM components had to show equivalent or better performance and durability to those components that were being replaced or the "Lifetime Service" would haunt us forever. The second consideration was to determine if the change was too radical a departure from S&W mainstream design.

For the performance and durability issues we decided that if MIM could be used for the fabrication of revolver hammers and triggers successfully this would truly be an "Acid Test". There is nothing more important to a revolvers feel than the all-important Single Action Sear that is established between the hammer and the trigger. Mechanically few places in a revolver work harder than at the point where the hammer and trigger bear against each other. If these surfaces wear or loose there "edge" the "feel" is lost. Initial testing was on these two critical parts. Over time we arrived at a point where our best shooters could not tell the difference between a revolver with the old style hammer and trigger and the new MIM components. Special attention was given to their endurance when used in our very light Magnum J frames such as the early prototype 340 & 360 Sc's. None of our revolvers work their components harder than these small magnum revolvers. Throughout this testing MIM held strong and finally we determined that this change judged on the basis of durability and feel was a good one.

The second area of concern to S&W was our customer’s reaction to this departure from the traditional. Many heated, intense discussions resulted but in the end the decision was made to move ahead with MIM.
The issue of cost was only one of the considerations in making this decision. Equally as important was the issue of part-to-part uniformity and the result of this of course is Revolver-to-Revolver consistency. We found that revolvers that used MIM hammers and triggers required almost no Fitter intervention in those areas during final assembly and final inspection and Trigger Pull Monitor rejection rates dropped markedly on finished guns. From an internal process point of view it appeared a "Winner".

Lets shift gears for a moment and talk about the MIM process. It is unclear to me as to the reason for many of the negative feelings on the forum concerning MIM. Typically when people complain and aren't specific in the reason why, the problem is often created by a departure from the "Traditional". Perhaps that is indeed what is bothering some people when they view MIM.

The term MIM stands for Metal Injection Molding. It holds some similarities to Plastic Injection Molding and many differences as well. To start we would take a finally divided metal powder. This could be stainless or carbon steel. Today even Titanium is being used in some MIM fabrications. We would mix the metal powder and a thermoplastic binder (generally a Wax) forming slurry of sorts when heated and inject this mix into a precision mold and finally form what is known as a “Green Part". This part is roughly 30% larger than the finished part it will become at the end of the process. Interestingly enough the Green Part at this stage can be snapped in two with simple finger pressure. The Green Parts are then placed in a Sintering furnace filled with dry Hydrogen gas and the temperature is brought almost to the melting point of the metal being used. Over time the "Wax" in the Green Part is evaporated, the metal fuses and the part shrinks 30% to it's final correct dimensions. At this stage of the process the MIM part has developed 98 to 99%of the density of the older wrought materials and a metallurgy that is almost identical. Dimensionally it is finished and no machining is required. However the job is not yet done and the MIM parts are brought to our Heat Treat facility for hardening and in the case of Hammers and Triggers, Case Hardening. Depending on the particular metal alloy that was used at the start of the process we apply a heat treat process that is the same as would be used if the material were the older wrought style. Final hardness, Case thickness and core hardness are for the most part identical to parts manufactured the older way.

Lets look for a moment at how we achieve dimensional precision when comparing these 2 processes. The old parts were each machined from either bar stock or a forging. Each cut and every resulting dimension was subject to machine variations, Cutter wear, operator variations etc. If every operation was done exactly right each and every time and the cutter didn't let you down you would have produced a good part but sometimes this didn’t happen resulting in a rejected gun and rework or in the worst case an unhappy customer. With MIM parts you must still machine to very high tolerances and your cutters have to be perfect and your machinist has to be highly qualified but all of this only has to come together one time. That time is when the injection mold is made. Typically a mold for this process costs S&W between 30,000 and 50,000 dollars. Once it is perfect every part it makes mirrors this perfection and you have in my view a wonderful manufacturing process.

Hopefully this description will help us all better understand the MIM process.
Please forgive the spelling errors and misplaced punctuation. I have no spell checker on this and the phone continues to ring!

Have a Great Weekend,

Additional Point.
Currently S&W is paying about $1.20/Lb for stainless steel bar stock. Raw MIM stainless steel inject able material costs $10.00/Lb."
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Probable causes to a cylinder that doesn't open or close smoothly:

loose extractor rod
bent extractor rod
loose thumb piece nut
short or worn center pin
end shake cylinder or yoke
dirt under extractor
yoke out of adjustment
worn bolt
worn locking bolt
worn yoke button
worn yoke screw
tight yoke screw
ammunition rubs frame or primer flow
worn recoil plate firing pin bushing
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Flame cutting

Here is a picture of what flame cutting looks like. The gun is my 629 44 mag.
Flame or gas cutting is quite normal and is nothing to worry about. If a revolver has been fired it will have some degree of flame cutting. Flame cutting usually stops after a time and won't get any worse.

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DCU or timing

DCU (doesn't carry up) or basic timing is easy to check.

How I check basic timing is pretty easy to do. Without touching the cylinder or holding back the cylinder just gently cock the hammer slowly in single action, (on all stations) and see if the cylinder stop snaps in place before the hammer falls. When the trigger is pulled to the rear (MIM triggers will rotate the cylinder further when the trigger is pulled) and the cylinder stop didn't snap into the cylinder notch, then you have a problem.

One thing I must insist, before swapping the parts make sure it's not a loose fitting ejector causing your dry fire and poor carry up problems. This is true with non-pinned cylinders. Drop empty cases into the chambers then check your carry up. Sometimes the gun is fixed when cases are inserted in the chambers.

As the extractor ratchets, hand, and hand window wear, they get to a point where the hand won't rotate the cylinder far enough to allow the cylinder stop to snap in before the hammer drops (carry up condition in DA mode). This is not a hand length issue, it’s a hand width problem. If you take the side plate off and watch carefully in the hand window while pulling the trigger, you will see the hand cams off of the ratchets and the left side of the hand tip positions against the right section of the ratchets to rotate the cylinder those last few degrees.

Unless a gun has been fired a zillion times, the hand and the window seldom show wear, except for the left tip of the hand. Most times when you see a hand loose in the window, it's because it was shipped that way.
Factory hands run from about .093 to .095" and wide hands run about .098 to .100" There shouldn’t be more than .001 side play between the hand and window.

If the hand has worn thinner, or the hand window has worn wider, or the edges of the ratchets have worn thinner, you will start loosing carry up. Without fail, the ratchets are the most usual cause.

There are several solutions. The absolute best one is to replace the extractor (ratchets). Unfortunately, that’s a factory fitted part and you can't buy one without sending the gun back to the factory.

The next best option is to fit a wider hand. This will have nearly the same effect as a new extractor because it will take up the slack from ratchet wear and make the cylinder rotate a few more degrees. When the wider hand is fitted, you must widen the left edge of the hand window so the hand will be positioned a few thousands to the left.

An undesirable option is to lay a fine bead of weld on the right edge of the hand window then dress some material from the left edge of the window. This will position the hand closer to the ratchet and make the cylinder rotate further. Welding that thin of metal is sure to do some damage to the finish and could ruin the frame.

You can bend the tip of the hand slightly to the left. This will also cause the cylinder to rotate a bit father. The hand is made of some very hard material and will fracture if you try to bend it without first softening it. You have to heat the tip of the hand until it is red hot then let it cool to room temperature. It will then be soft enough to bend without breaking. Once you get the hand tip bent, you must re-harden the hand. Herein lies the problem. Most of us don't have the proper metallurgy skills to re-harden the hand. If it is soft, it will soon wear out.

One of the very precision specs in an S&W revolver is the hand-to-ratchet clearance. A few thousandths makes the difference between good and bad carry up. You want the hand tip to be touching the ratchet but not binding on it when the trigger is pulled. Basically a zero clearance.

If you insert the tip of the hand into the window, it should move freely with minimal side play. The tighter the better, as long as it doesn't bind.

The left side of the window creates a reference point in respect to the ratchets. You must move the reference point to the left before the wide hand will make the cylinder rotate more. That means you must take metal off of the left side of the window. Use a "safe" window file for this. Taking metal off the hand or the right side of the window moves the reference point the wrong way.

Once your wide hand is installed, the tip of the hand may bind on some of the ratchets. This will cause a bad gag in DA trigger pull. With the side plate off, watch through the hand window as you cycle the gun in DA. You will see where the hand cams off of the ratchet and the point of contact between the hand tip and each ratchet. Dress the ratchets at the point of contact so the hand is touching but not binding.

Go slowly changing the hand. It's easy to do and will fix your timing (DCU) problems.
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To correct push off

The hammer notch must be square, sharp and not rounded. It's only .005 inch tall so use a eye loupe to inspect it. Use a new stone to true it up, if it's not square. (I like ceramic stones for this) Then after the hammer is proper, stoning the trigger will correct the push off.

Remember use a 6 inch long stone. Changing the stone length will affect the trigger pull.

To test the trigger hook, you scrap it on your thumb nail. If nail is scraped off, you got it sharpened correctly.

If you want a lighter single action pull, you dull the angle by lightly stoning the angle parallel to the table top.
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New style firing pin removal

When you pull the side plate off, the upper pin (that aligns the plate) is the firing pin retainer. Remove the pin, spring and firing pin will come out.

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Find a perfect fitting screwdriver.

Remove the grip.

Unscrew all the screws on the side plate, don't mix them up.

Roll gun over, push the thumb latch in and open the cylinder.

Slide yoke and cylinder off the frame, go easy not to scratch it.

Roll gun back and find a plastic hammer and tap the frame (near where the grips would be) and the side plate will come loose.

Remove slide plate.

Lift out the hammer block (sheet metal part with a hole on one end, hook on the other).

Loosen strain screw and remove main spring. (J frame insert cotter pin into hole, remove from stirrup).

Pull thumb piece to rear. Press trigger to cock hammer, lift hammer up and off the stud.

Find a screwdriver, and pry the rebound slide off the stud, rebound spring and stem will fly out so keep a finger over opening.

Pull back the hand to clear window, then wiggle trigger off the stud.

You can remove the cylinder stop and bolt but the gains are not worth the trouble.

But if you must, then flip gun over and unscrew thumb piece.

Flip gun back, pull bolt to rear and lift out of frame, watch out for plunger and tiny spring.

Pry out spring for cylinder stop, let the stop drop down and remove stop.

Reverse the operation to put it back together. Find a special rebound slide tool to put the rebound spring back on. It looks like this:

Remember all the guns from J frame to X are nearly all the same internally.

The hammer block sits all the way up before the slide plate goes back on. One end sits on the stud of the rebound slide, the other end sits in front of the hammer. Picture of 500:

Here is a picture of a 686 without the hammer block:


Once the cylinder in on the table it can be totally taken apart.
Guns which are about 40 years and newer the ejector rod is counter-clockwise. Older than this the threads are clockwise.

Place empty cartridges into the cylinder.

Using a drill chuck, turn extractor rod and unscrew it. (Don't mar the knurl on the end)
There are 2 springs inside, a collar, center pin and the ratchet. Keep finger pressure on the ejector rod so the springs don't fly off the table.

Reassemble in the reverse order. You don't need lock tite on the threads.

You could use a tool like this instead of the drill chuck, if you prefer:


Here is a picture of what the parts look like.

To disassemble: turn knurled end clockwise, remove nut and slide the yoke off. Be careful not to mar the knurl. I use a clothes pin under pliers.
Then using a drill chuck, turn extractor rod clockwise to remove the extractor assembly.

(all threads are counter-clockwise)

Here is a picture of all the J frame parts spread out for your pleasure.

The larger frames K,L & N have an additional part called the extractor rod collar. This part shows in the earlier diagram of the model 29 I posted earlier.
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