Cylinder fitting

[parastein]

Hey all - I'm planning to get an M&P 340 and swap a Ti cylinder to it immediately, letting me get the better sights with PD weight. I've had a revolver in the past but am not a "revolver guy".

I've heard I can save some grief by keeping the extractor from the fitted cylinder when I swap to the Ti cylinder. My plan is then to check the headspace (rear) and gap (front) with some feeler gauges, that the endshake is acceptable, and that the timing seems alright.

I'm somewhat mechanically inclined and glad to buy a few tools, or even shim if necessary, but am I insane to do so from internet research alone? Is it worth sending to S&W to have it fitted to preserve the warranty (assuming I buy new)? I don't know of any trustworthy revolver gunsmiths here but of course I can try to find one, or take recommendations online, but I'm not even sure how much I should spend on this.

If I DIY this, and it looks good to my eye, what is the worst outcome if I'm wrong and go shoot it?

 

[stansdds]

Welcome to the S&W Forums. Maybe I'm mistaken, but don't the current crop of 340's come with front sights that are pinned to the barrel? Seems to me if you want a lightweight 357 J-frame, it would be easier and less expensive to get the 340PD and change the front sight.

 

[armorer951]

Strictly my opinion here, but personally, for safety reasons, I would not recommend this particular project as your very first venture into the world of revolver modifications and repairs.

The net gain, or loss, depending how you look at it, of this potentially expensive "roller coaster" ride would be the reduction in weight of the recipient revolver by the removal of approx 52 grams, or 1.83 ounces of weight by substituting the Titanium cylinder. You could contact the factory, but I'm not sure they would agree to switch the cylinders for you.

On occasion, cylinders from current production revolvers can be moved from one compatible to another without incident. The problem comes when intervention and fitting are required....and evaluation and safety checks have to be done prior to test firing. These steps often require specific fitting of components, and specialized tools and experience.

Perhaps a good start would be Jerry Kuhnhauses's book on the Smith and Wesson Revolvers, A Shop Manual, and then take on some projects as you gain confidence with the internals and all of the tools required.
This would be a great step in learning more about these revolvers, and in making yourself somewhat "autonomous" from factory or gunsmith intervention when simple repairs are required.

Worst case scenario as a DIY is potential personal injury or worse, and a boatload of personal liability.



Carter

 

[-BTM-]

How do you plan to check the timing? Seems like a lot to save 3 ounces.

 

[StrawHat]

…

I don't know of any trustworthy revolver gunsmiths here…

Unless you tell us where “here” is, we can not recommend anyone even remotely local.

There are several notable gunsmiths still working around the country.

Kevin

 

[parastein]

Appreciate on the input so far.

I appreciate that the gain is "only" a few ounces. In fact, that is the only reason I'm doing it - to get the gun as light as possible.

The 340PD has a square rear "notch", while the M&P 340 has a rear U-notch, that most all users have said is far superior especially when used with the XS dot sights, hence doing it this way. I figured that swapping the cylinder on an M&P is easier than correctly grinding a U-notch into a 340 PD. I also found that sight installation on the 340 PD was less than straightforward, and could involve lots of hand fitting and require a drill press, which is definitely more expensive than some files, feeler gauges and bespoke tools (or even gunsmith hours).

Regarding the timing, keeping the same extractor that came with the gun when swapping to the Ti cylinder seems like it should keep me above board, but I've seen some videos from MidwayUSA and others on checking that it's achieving lockup before firing on all cylinders, etc. I'm not sure how complicated it is.

There are quite a few threads on this forum which gave me this idea, hence why I'm posting about it now, so I'm a bit surprised to hear that this is such an outlandish notion. The fact that S&W even sells the titanium cylinder also seems to hint that this is a not-uncommon thing to do.

There's a 3 page thread here for all the people who've done this with a 442.

https://smith-wessonforum.com/s-w-r...42-a.html?highlight=fitting+titanium+cylinder

Questions On Fitting Ti cylinder to M442-2

fitting replacement cylinder

 

[parastein]

Unless you tell us where “here” is, we can not recommend anyone even remotely local.

There are several notable gunsmiths still working around the country.

Kevin

Apologies - I'm in Washington. I see TK Customs does lots of custom cylinder work by mail, I may ask if they're willing to do fitting. I don't have a problem shipping it to someone good. I also seem to have read in some of the linked threads that people had S&W do this fitting for them.

 

[StrawHat]

Andy Horvath, here in LaGrange, Ohio.
There are a couple of fellows in Arizona, but their names escape me. Frank Glenn?

Others will be along to provide additional information.

Kevin

 

[smoothshooter]

I don’t think I would go to all that trouble to save a couple of ounces gun weight.
I don’t know of anyone who actually enjoys shooting full-powered .357 loads in a super light gun anyway.
Less recoil will make you want to practice more and be a better shooter.

 

[Shotguncoach]

I would agree with the advice not to attempt this as your first project. I worked for a year and got lots of instruction/advice from others before I was able to successfully fit a brand new cylinder. My advice would be to work up to it. You have a working gun now....do some other projects on junky guns before you tackle the nice one. If you're not interested in training that long, that's what gunsmiths are for.

 

[parastein]

I would agree with the advice not to attempt this as your first project. I worked for a year and got lots of instruction/advice from others before I was able to successfully fit a brand new cylinder. My advice would be to work up to it. You have a working gun now....do some other projects on junky guns before you tackle the nice one. If you're not interested in training that long, that's what gunsmiths are for.

I don't actually have a working gun yet, I'm still figuring out how I'm gonna go about this.

I'll be honest, I have a lot of hobbies, and working on revolvers isn't one of them nor am I planning to add it. If swapping a cylinder but keeping the extractor and checking headspace and endshake isn't 99% likely to be all thats needed here then maybe I will just get a 340 PD.

Funny enough, buying a 340 M&P and a Titanium cylinder is nearly $100 cheaper than buying a 340PD, and that's ignoring also buying XS sights for the 340PD.

 

[Beju]

The 340PD has a square rear "notch", while the M&P 340 has a rear U-notch, that most all users have said is far superior especially when used with the XS dot sights, hence doing it this way. I figured that swapping the cylinder on an M&P is easier than correctly grinding a U-notch into a 340 PD.

FWIW, I haven't done this exact experiment, but I do have a Ruger LCR that I installed an XS standard dot on, and I have a 442UC and a 642UC.

I definitely felt like I lost some ultimate precision with the LCR when slow firing after swapping from the front blade sight to the XS dot, and some of that probably has to do with using a dot sight and a square rear ditch sight. However, it was better in the quick shooting inside 7 yards that will make up the vast majority of defensive gun uses.

The U-notch rear sights of the UC guns make shooting past 7 yards easier and more intuitive for me, and do the same for smaller groups at all distances.

 

[magnum0710]

I'm not sure about new production guns so someone correct me if I'm wrong but sometimes keeping the original extractor may not be possible. I restored my Ruger Speed Six and did a cylinder swap, the alignment pins for the star were in different spots on the replacement so using the original extractor wasn't an option. Luckily I didn't need to use the original extractor but it doesn't always work like that. I believe if you buy a brand new cylinder it has to be fitted and timed to your gun. Now what you could do is try and find a used titanium cylinder and use your original yoke and crane. If you're able to use the original extractor that would greatly increase your chances but it's not a guarantee. Perhaps getting a parts gun that has the titanium cylinder and the hand it was originally timed to would help. I pretty much had to do the swap on my Speed Six otherwise I wouldn't have taken the chance. Using my original crane and yoke worked perfect but I had to make sure I got a cylinder that was made around the same time as my gun. Ruger doesn't note changes like S&W does. Much like the K frames the gas ring was moved from the yoke to the front of the cylinder on the late model Six revolvers. I had to make sure the cylinder I got had the gas ring on the cylinder because the dimensions are slightly different. I also bought the trigger assembly from the same gun the new cylinder came from just incase I need the hand it was originally timed and fitted to. Luckily I didn't and my original parts worked but a drop in fit is never a guarantee.

Your best bet would be to buy a used cylinder and use as many of the original parts from your gun as possible. The yoke and crane especially but if you can use your original extractor that's even better. Worst case you need to have it fitted by a gunsmith.

In your case I agree with the others, it's not really worth the trouble. You're only going to save about an ounce of weight, the M&P is extremely light for a 357 as it is even with a steel cylinder. 357 isn't going to be pleasant as it is, dropping the weight further will make it worse. It's already going to beat up your hand like you owe it money. Honestly I wish they'd bring back the m&p 360. My only option now is the PD unless I find a used standard 360.

 

[BLUEDOT37]

Everyone has to know their own limits but if you "feel" comfortable with it, after researching the subject, go for it, knowing & owning the responsibilities.

However, I'd thoroughly test fire the new revolver with an assortment of ammo you intend to use in it before you do the cylinder swap to sort out any issues with the new revolver & not confuse things by starting off with a transplanted part in it.

After test firing is successfully completed then check the cylinder-barrel gap & endshake clearances before doing the swap.

I've swapped out cylinders on several revolvers, including a J-frame, & reused the original extractor assembly each time. Only once I had to add a spacer/shim/bearing to fix the added endshake issue, which is an easy process, but don't make it too tight either.

Timing should be correct if you reuse the original extractor, unless something is "off" with the new cylinder, but check things closely afterwards of course.

Be safe & don't hesitate to have a gunsmith do the job if you find you bit off more than you can chew.

.

 

[atlatl]

FWIW, I have done exactly what you intend to do three times, twice for my self once for a friend. One time I needed an end shake washer, one time I needed to file the rear of the barrel a couple thousands and once was a drop in fit. I did this shortly after the "no lock" M&P 340s were introduced.

I did it to get exactly what I wanted and every time I carry the revolver I am happy with it.

If you understand the relationship of the parts it's not a big deal.

 

[parastein]

FWIW, I have done exactly what you intend to do three times, twice for my self once for a friend. One time I needed an end shake washer, one time I needed to file the rear of the barrel a couple thousands and once was a drop in fit. I did this shortly after the "no lock" M&P 340s were introduced.

I did it to get exactly what I wanted and every time I carry the revolver I am happy with it.

If you understand the relationship of the parts it's not a big deal.

Thanks. Pulled the trigger on a new M&P 340 and have a cylinder on the way, we'll see how it goes.

 

[parastein]

Gun and cylinder were fit together and shot. Gap came in at around .004-.005, with the tightest chamber being .003 from the right and .004 from the left. It seems as though the forcing cone wasn't faced off perfectly flat.

Factory gap was around .08-.010.

This cylinder on my calipers shows as being .003 longer than the factory one.

No endshake of note. Reused original extractor star.

Anything I can or should do about the forcing cone face?

 

[stansdds]

It's not uncommon for the forcing cone to not be perfectly square with the cylinder. I don't think I would worry about that 0.001" difference.

 

[sandog]

Anything I can or should do about the forcing cone face?

I'd use a Brownells 90 degree cutter, with a .38 cal. brass guide in the bore.
A gunsmith would likely do the same, much easier than removing the barrel and the 90 degree cutter will give you a nice square barrel end.

This is the set-up used, but here a 11 degree cutter is being used to re-cut a short/shallow forcing cone.
Put the rod w/ brass spacer into the barrel. then thread on the cutter inside the cylinder opening.

With 3 or 4 cutters (not cheap, around $50 each) and a rod, handle and a few brass guides in various calibers, you can do a lot of jobs yourself.
Here a 45 degree cutter with brass guide was used to chamfer the sharp edge of each chamber for easier loading.

 

[jcelect]

Gun and cylinder were fit together and shot. Gap came in at around .004-.005, with the tightest chamber being .003 from the right and .004 from the left. It seems as though the forcing cone wasn't faced off perfectly flat.

Factory gap was around .08-.010.

This cylinder on my calipers shows as being .003 longer than the factory one.

No endshake of note. Reused original extractor star.

Anything I can or should do about the forcing cone face?

This is probably the most important part of a cylinder swap! A .003"-.004" BC gap is too tight! Powder residue and/or lead on the front of the cylinder will stop the cylinder from turning at some point in time. sandog posted a pic of the tool you will need. There is a flat cutter attachment that will cut and square up the breech end of the barrel. A file is probably the worst tool to use here! Then you will need to recut the forcing cone(the tapper inside of the barrel at the breech). Also, you will need a set of go/no go gauges to determine the proper depth of the forcing cone. The only thing that is quick and easy in working with guns is ruining one by making a mistake! The required tools ain't cheap, unless you are going to do more guns!
jcelect