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View Full Version : Installing a new barrel in a S&W M629


ChrisR
April 10, 2009, 07:13 PM
I have my eye on a 8" M629 - I'm wondering about the process involved in fitting a 4" barrel. I have the S&W revolver shop manual coming but in the meantime I would be interested in the process and techniques/tools used etc if anyone has some spare time and cares to volunteer. And no don't worry I'm noting going to go at it with a hammer and vice and hacksaw, I'd just like an overview if possible.

James K
April 10, 2009, 07:26 PM
Barrel work on that revolver requires both a barrel vise and a receiver wrench specially made (or with inserts specially made) for that frame and that barrel. That kind of equipment costs more than the cost would be for someone already set up to do the job; unfortunately, there are very few gunsmiths who have the proper equipment.

Frankly, I would call S&W or Cylinder & Slide, but the latter is heavily backlogged. That barrel swap is NOT, IMHO, any kind of a DIY job. In the old days of pinned barrels, a lot of gunsmiths used a barrel vise and a hammer handle or a piece of 1x1 wood. With torqued barrels, that technique will only bend the frame.

Jim

ChrisR
April 10, 2009, 09:21 PM
Ok, thanks. I guess I should look for another revolver in that case as sending to those outfits is not an option (from New Zealand). Pity because the revolver I have in mind is mint and well priced.

steveracer
April 24, 2009, 07:18 PM
Will cost less, too. Most decent smiths can chop a barrel, recrown, and install a new front sight for ~200.
Steve

Dfariswheel
April 24, 2009, 07:35 PM
Here's something I wrote about how to re-barrel a revolver, and some "watch outs".

Changing a revolver barrel
A common question is “How do I change my revolvers barrel”?

Barrel work is a MAJOR pistolsmithing job and requires a considerable amount of very expensive equipment.
It involves a lot of steps that most people, including a surprising number of gunsmiths, don’t even know is required.
Failure to do the job correctly insures an inaccurate revolver at best, and a destroyed frame at worst.

The common do-it-yourself technique is to use “expedient” tooling techniques that are found in old gunsmithing books, and can still be found mentioned occasionally in gun magazines.
These methods range from wrapping rope around the barrel and using it with a stick to form a sort of tourniquet to unscrew the barrel, to the most common, which is to use a hammer handle through the frame window as a “wrench”.

The hammer handle method is to make up a pair of wood barrel blocks for the barrel.
The barrel is sandwiched between the blocks, and are locked in a shop vice. One writer said to “Tighten the vise until your eyes bugged out”.
A hammer handle or a shaped wooden 2x4 is shoved through the frame and is used as a “wrench” to twist the frame off.
The new barrel is fitted by hand filing the barrel shoulder until the front sight is at 12:00, the rear of the barrel is filed, if necessary, to provide a small gap between the barrel and the cylinder, and you’re off to the range to shoot your fresh re-barrel.

At least that’s how it’s touted as working.

In reality, when the hammer handle is used to turn the frame, one of two things happen:
Either the frame bends, or it breaks.
Revolver frames are a lot softer and easier to bend then most people suspect, and when the frame itself is used as a wrench, the frame will almost always bend.
Once bent, the frame is ruined even though it may still be shoot-able.
A bent frame will often have timing problems, and always has alignment problems. All of which cause inaccuracy and possible spitting of bullet metal.
Some owners who’ve tried this method of barrel work, are surprised that the factories do not have some kind of machine or device that will straighten the frame like bent car frames can sometimes be straightened.
The fact is, once bent the frame can never be repaired, and the best a factory can do is replace it.

The second thing that can happen is the frame will break.
If you look at a revolver frame just under the area where the barrel screws in, you’ll see that the frame is very thin in this area.
When the unsupported frame is unscrewed with the handle, it can crack right through the threaded portion.
While there are ways to weld the crack, the very high expense of having a top level custom pistolsmith/welder do it is very prohibitive, and is reserved for repairs to revolvers of high historical value, with NO guarantee that it will work.

The advice to hand file the barrel shoulder to align the barrel and to file the end of the barrel to provide the barrel/cylinder gap always ruins the barrel, since it’s near impossible to keep the surfaces perfectly square.
The result is tilted barrels due to uneven shoulders, and the end of the barrel not square with the cylinder.

When re-barreling a revolver, the first thing you need is a USABLE barrel.
This is much harder to get then you’d think, since a good percentage of barrels for sale at gun shows and on eBay are defective.
Major reasons for selling a used barrel are, the barrel was defective to start with, or it was damaged during removal, using the hammer handle method.
This damage may not always be readily apparent, and sometimes isn’t revealed until the pistolsmith attempts to install it.
Damage can run from tiny cracks in the forcing cone to pitted bores, to bent barrels.
I once saw a Diamondback barrel that someone had TWISTED, probably by attempting to unscrew it from the frame the wrong way.
This wasn’t apparent until, suspicious, I checked it with a straight edge.

Cracks in the forcing cone are common, and contrary to popular opinion, a cracked barrel is almost always toast.
Cracks in steel tend to continue to spread, even if you cut the cracked end off, since cracks are a sign of metal fatigue caused by blast damage.
Some gunsmiths will attempt to save a barrel with a cracked forcing cone by setting the barrel back, but this almost always fails, and the crack continues to spread forward.

Here’s a brief description of how a revolver barrel is changed correctly:
First, the barrel is locked in a special barrel vise.
I had two, one was a small scale copy of the larger hydraulic jack type vises that gunsmiths use to change out rifle barrels.
I used this one for older round barrels like the Colt Official Police.
The second vise was large Wilton vise with heavily modified jaws.
I had sets of custom machined brass or aluminum barrel inserts that were fitted to specific makes and models.
As example I had sets for Pythons, Trooper Mark III’s, King Cobras, shrouded Detective Specials, etc.
These inserts are installed around the barrel, then clamped in the barrel vise.

The action, or frame wrench, is installed on the frame.
This wrench is a universal revolver wrench that fits around the front of the frame. It is fitted with brand and type specific hard plastic inserts.
These inserts very closely fit the front of the frame around and below the barrel area to fully support the frame.
Again, I had inserts for specific guns. I had one set for Colt “E & I” frames, another set for “J” frames, another set for “D” frames, etc.
These inserts support the frame and spread the torque over a wider area to allow unscrewing the frame without over stressing the frame and damaging it.

With the frame and barrel tightly locked up, and with no “spring” to the setup, the frame is unscrewed from the barrel

With the barrel off, the frame threads are cleaned up with brass brushes, solvent, and if necessary are “chased” with a tap to insure clean, uniform threads.
The replacement barrel is closely inspected and it’s threads are cleaned and chased with a die if necessary.

The barrel is test fitted to the frame to determine where the front sight is and how much material has to be removed to allow the front sight to be at 12:00 top-dead-center after being torqued in place.
How much to remove is largely a judgment call based on experience.
Using a lathe or a bench trimming device, that amount of metal is removed from the barrel shoulder.
The barrel threads are coated with anti-seize compound and the barrel is threaded on the frame, everything is relocked in the barrel vise and frame wrench, and the barrel is torqued in place.
If the barrel is torqued with insufficient torque the barrel will vibrate loose.
Too much and you run the risk of pressure dimpling or constricting the bore in the thread area, or even cracking the frame.

With the barrel in place, the barrel/cylinder gap must be set.
This is done with a special cutter tool that works down the bore.
A Tee-handle rod is put down the bore and a cutter tool is attached on the end. The rod is pulled outward and rotated, trimming the end of the barrel.
Care has to be taken to insure the end of the barrel is not scalloped from uneven pressure.

With the barrel/cylinder gap set to an ideal .005”, the forcing cone has to be re-cut.
The forcing cone is very misunderstood, and even some gunsmiths have no idea it has to be re-cut and gaged or that it must be gaged at all.
The critical dimension of the cone is not it’s “length” or taper, but the outer diameter of the mouth.
If the outer mouth is too big, the gun will be inaccurate. Too small and it’s inaccurate AND will spit bullet metal.

The same Tee handle tool is inserted down the bore, but this time a cone-shaped cutter head is attached.
The cutter heads come in various tapers, and you can set a barrel for exclusive use with lead bullets by using a longer taper, or for jacketed with shorter tapers.
The factories use a good compromise that works with everything.
The Tee handle is pulled outward, pulling the cutter into the forcing cone. The handle is rotated and the cutter head cuts the cone.
Again, care is taken to prevent scalloping and the progress is checked often with a special plug gage.
This drop-in plug gage gages the outer diameter of the cone. The difference between too large and too small is very small, so gauging is done often.
The cone cannot be "eyeballed", it has to be gaged.

After the cone is cut, yet another head is attached to the Tee handle, this time a brass cone-shaped lapping head.
Valve grinding compound is applied to the lap, and the forcing cone is lapped to a smooth finish.

After lapping, the barrel and frame is carefully cleaned of all metal chips and lapping compound, and the revolver is reassembled.
The last step is firing the revolver for function, and to check accuracy off the sandbags.

As you can see, there’s a LOT more involved than first thought, and all steps are CRITICAL.
Unless you’re willing to invest quite a bit of money in custom made tooling and spend the time learning how to properly use it, attempting a do-it-yourself re-barrel job is a very fast way to ruin a good gun.

SCMA-1
April 25, 2009, 10:17 AM
I'm in a similar boat; I have a 629 Classic Hunter w/8-3/8" barrel and would like to purchase and install a 6.5" barrel that I found. My model number is 629-2E. The barrel I will be swapping is for a 629-4 or 629-5. Remember that these barrels have a full length underlug (ejector shroud).

My questions: Are all 629 barrels interchangeable despite the difference in the model number after the dash? Also, considering that I find a qualified smith to do the work as Dfariswheel has outlined; typically how much does this job cost?

I hope this doesn't constitute "thread jacking" and if it does, please accept my apologies.

Thanks!

SCMA-1

Dfariswheel
April 25, 2009, 06:46 PM
"As I recall" (Note the qualifier) the barrels should be compatible.

I'd suggest talking to S&W about doing it. They have the special tools and know all about how to do it.

If not S&W, talk to Cylinder & Slide Shop. They'll cost more and take longer, but do factory level work.

James K
April 26, 2009, 09:57 PM
I just read Dfariswheel's excellent post.

See how easy it is? Like your cousin Bubba says, just get a vise and a pipe wrench and have at it!

Jim

ChrisR
April 29, 2009, 01:38 PM
I read that excellent post and the S&W shop manual - I have the tooling I need to fit the barrel (wrench/insert). I can make the barrel block though will need to buy the tools to trim the barrel to obtain the correct cylinder clearance and recut the forcing cone etc.

Question - how does one hold a non cylindrical barrel in a lathe or similar in order to trim the shoulder? Also, where does one find the torque specs for my barrel/frame?

ChrisR
April 30, 2009, 12:23 AM
Ok, so you buy a shoulder trimming device from Brownells or similar...