Rechambering a junk 38-40 New Service to 40 S&W?

[blackhawk38wcf]

After reading the various threads regarding the different 10mm type revolvers, I had an inspiration.  I commented about the Chiappa 40 being used and someone remarked how thin the walls of the cylinder would be on that revolver.  But they do make it in 40 S&W so the thin-ness of the cylinder wasn't an issue. However, what surprised me was that Chiappa used a form of high tensile strength aluminum as a basis for the frame of that revolver.  This could withstand the pressures of the 40 S&W cartridge, which operates nominally around 33-35 KPsi. I also thought "didn't the New Service have models made or converted to 357 Magnum, which is basically the same pressure as the 40?"  Conversely, Chiappa also makes their revolver in 357 Magnum.  In the past, M1917 revolvers were remade into 357 Magnum revolvers using a Numrich Arms conversion kit.  May of these converts still are safely used today. Well, if this type of conversion is fine for the M1917, why not a conventional 38-40 New Service? After all, the ordnance steel used in that era seems to be tough enough to safely shoot a 357 ctg.  I do have a spare 357 Magnum cylinder for a New Service that I can have rechambered to 40 S&W.  And, the 38-40 N.S. I have has a stainless steel heavy barrel on it (don't ask why. I bought it that way).  But the cylinder is loose and likely needs replacing.  So there is no collector value on the New Service.  Well, as I am apprehensive about this type of conversions, putting this information together theoretically makes sense.  With the Chiappa in the 1000 range and the 610s subject to bidding wars and out of my price range, a conversion of this revolver to 40 Smith might be a solution. What do you think? BH38WCF.

[The_Shadow]

To 40S&W you could probably do it, if I recall you can cut the cylinder to head space on the case mouth and not need any moon clips which don't work on an old single action type.  There are many thing that can be done with money and tooling.

It was I that mentioned the cylinder thickness, thinking that they wanted to convert it to 10mm from 40S&W, if cutting the cylinder for head spacing for 10mm the 40's will no longer be an option with out cutting the cylinder to accommodate the moon clips.  This is assuming the cylinder could handle the extra pressure of 10mm.

I know some have re-worked the Ruger Sp101 357 to make it a 10mm, but don't know all that was done to make it work, was the 357 cylinder just bored to 10mm? or if they had a new cylinder made, or if they used moon clips to be able to shoot the 40's.

[DM1906]

It's more than just pressure. The smaller cylindrical diameter of the .357 will offset any overall pressure differential, but the displacement/PSI requires different engineering, especially when using unique/unorthodox metallurgy. The .357M in full trim operates at 36-40K PSI. Also, "rechambering" the .38-40 to any other modern .40 caliber can't be done, as the chamber of the .38-40 is larger. A new cylinder can be cut to any caliber or cartridge, of course.

Also, there are options other than moon clips, for using rimless cases in revolvers, despite the headspacing method. Some so simple, you'll have a "duh" moment. I shoot .40SW in my 10mm RBH cylinder, all day long. Same shooting .45ACP (not auto-rim) in the .45LC RBH. .32ACP in your .327FM or .32C? No problem. 9mm in your .357M (NOT .38spl), the same. All day long.

[sqlbullet]

Let me make sure I get this right.

We are using a 38-40 New Service as the base gun, but not using the 38-40 cylinder.  The cylinder will be obtained by boring and reaming a spare New Service 357 mag cylinder.  If this isn't what I was supposed to derive from the original post, please clear it up.

My first thought was the same as DM1906; you can't re-bore a 38-40 to 40 S&W or 10mm as the base diameter of the 38-40 is a good bit larger than 40/10mm.

But, I think you are suggesting using a 357 mag cylinder with a 38-40 frame/barrel.  While I don't doubt a 40 S&W cylinder can be created, I don't know if a 357 cylinder would be the right starting point.  Best to contact a knowledgable gunsmith with a rich history in caliber conversions.

Given that the bids 38-40 New Service or M1917 seem to be around $600-$800 and that Bowen charges $750 for this type of conversion to your gun, I think you would be better served to sell your New Service and start shopping for a $1000-$1200 610. 

[blackhawk38wcf]

Hi DM1906, you have the first portion of the message correct. But you also mentioned that "Given that the bids 38-40 New Service or M1917 seem to be around $600-$800 and that Bowen charges $750 for this type of conversion to your gun, I think you would be better served to sell your New Service and start shopping for a $1000-$1200 610."  Uh, no.  First off, try more like $1500 for a 610 just for starts. 2nd, the title of the post was a "junk 38-40." Due to the previous work done on this revolver I previously stated, the estimated collector value stated here doesn't apply.  This is approximately a $150-250 dollar gun (in fact, I think I bought it midrange of this pricing), especially with the 7.5" stainless .401" barrel installed. Not only that, the 38-40 cylinder is well worn.  The rest of the New Service appears tight and the barrel seems to be good and nearly new.  Besides, a typical rechambering of a cylinder can run around $200-300 depending on the 'smith doing the work. Even if the work totaled $700 everything included, it would be worth it for obvious reasons. In fact, I'm working on a variation of the theme. Stay tuned. BH38WCF. 

[DM1906]

The Colt New Service revolver is a fine handgun, but it was designed for turn-of-the-century cartridges. Suggesting using one, in any bore, for 10mm pressures is ill-advised. All of the chamberings of early models were limited to less than 20K PSI, and less for "big bore" cartridges (any larger than .378"), most never graduating from black powder until very recently. Also note, the cylindrical diameter of the cartridge determines force applied to the breach, comparable within similar case volume pressure/dwell maps. While the .357M operates at a significantly higher pressure than the .40SW, and somewhat higher than the 10mm Auto (previous .357M ANSI/SAAMI spec of 40K PSI), the .357M cartridge imparts significantly less force-energy upon the breach than the others, due to the cylindrical diameter and greater case volume. At most, it would be comparable. Incidental metallurgical advances notwithstanding, the "New Model" was only "new", compared to mid-19th century designs. New Model .38-40 and .45LC pistols, for example, are still limited to 1890 design pressures, while Ruger Blackhawks (New Model Vaquero excluded) easily manage 32K-40K PSI big bores. It is my opinion that a Colt revolver, including clones, should never be considered a baseline for uprating. There may be exceptions, of course, but none relating to this discussion.

Other factors to consider, when considering other ".40" caliber cartridges is, the actual bores of these calibers. None but the most recent cartridges were actually a .40" bore. They varied from .340" to .419" (many of them previously pin-fire and rimfire), some requiring specific bullet designs. For example, an original .401 Herter's PM is actually a .403" bore, which removes it from the ideal category for any current jacketed .40 caliber bullet, and all but custom cast lead bullets.

As SQL said, conversions are rarely cost effective, if a factory offering for a cartridge is offered, in any caliber. There are several better options to choose from, that don't include redesigning a cylinder, especially one that was never developed to withstand the pressures involved. As he said, simply reaming a chamber of a .40SW is a much better option than any other, in nearly every case. If cartridge versatility is desired, D/A revolvers are the least practical and most costly to consider. If Dan Wesson or Ruger didn't offer it, there was probably a very good reason.

[DM1906]

Hi DM1906, you have the first portion of the message correct. But you also mentioned that "Given that the bids 38-40 New Service or M1917 seem to be around $600-$800 and that Bowen charges $750 for this type of conversion to your gun, I think you would be better served to sell your New Service and start shopping for a $1000-$1200 610."  Uh, no.  First off, try more like $1500 for a 610 just for starts. 2nd, the title of the post was a "junk 38-40." Due to the previous work done on this revolver I previously stated, the estimated collector value stated here doesn't apply.  This is approximately a $150-250 dollar gun (in fact, I think I bought it midrange of this pricing), especially with the 7.5" stainless .401" barrel installed. Not only that, the 38-40 cylinder is well worn.  The rest of the New Service appears tight and the barrel seems to be good and nearly new.  Besides, a typical rechambering of a cylinder can run around $200-300 depending on the 'smith doing the work. Even if the work totaled $700 everything included, it would be worth it for obvious reasons. In fact, I'm working on a variation of the theme. Stay tuned. BH38WCF.

That wasn't my quote, but I don't disagree with Shadow or SQL. Consistent with my previous posts, it would be cost prohibitive because the base model you've chosen is not suitable for your intention. I didn't address the cost factor, originally because, well, it's your money and you can do with it as you wish. My interest, and specialty, is the science. You can spend money in any which way, but the laws of physics, in regards to ballistic pyrotechnics and metallurgy, are quite constant.

[sqlbullet]

I consider being confused for DM1906 good praise for me.

The $1000-$1200 suggesting isn't a pipe dream.  I agree that most 610's go for more than that in the "buy it now" category.  But I picked those numbers because I found finalized auctions on them on gunbroker in the last couple month for those amounts.  Most of the guns above $1500 are unfired safe queens, and it appears a bunch of the last batch of 610's were purchased by guys hoping to sell them speculatively.  But deals can be found if you are willing to shop for a couple months diligently.

http://www.gunbroker.com/Auction/ViewItem.aspx?Item=354781602

http://www.gunbroker.com/Auction/ViewItem.aspx?Item=349437186

And, as far as conversion goes, like DM1906 points out, a genuine New Service cylinder is likely not going to be suitable for 10mm.  Even a 357 mag cylinder probably can't just be pilot reamed or line bored.  It would probably need a new heat treat at the very least.  Most likely you are looking at a custom lathe turned cylinder from a suitable alloy, line bored, finish reamed, heat treated and then fitted to your gun.

But...I am no gunsmith.  Hence my suggestion that you get some actual estimates to make this happen, then decide what to do.

You also assert your gun is "no collector".  Again, the $600 to $800 was based on recently ended auctions on gunbroker that actually resulted in a sale.  If you cylinder is shot, track one down.  It should only cost about $150-$200 for a new cylinder.  If the rest of the gun is in good shape you would be offering a lower cost item on the auction sites once you had replaced the cylinder.

Like DM1906 says, you can do as you wish.  I was just offering you the benefit of some research on my nickel, and then my analytic take based on that research.

[blackhawk38wcf]

I beg to differ. Apparently,  you haven't carefully read my description of the gun.  I'm sure I can do way below the costs you think it would cost me.  You said it yourself: you are no gunsmith. Watch me. Besides, I never said anything about modifying the 357 cylinder to 10mm. Sincerely, BH38WCF.

[sqlbullet]

Let us know how it goes.

[blackhawk38wcf]

Got in contact with one 'smith who tentatively agreed to boring out my New Service cylinder. I have to supply him with the reamer before he can do the work. Stay tuned. BH38WCF.

[blackhawk38wcf]

Mission accomplished! I now possess the world's first Col New Service in 40S&W! And can she shoot. Pix available but I need to upload them.

[sqlbullet]

Congrats.

I would love to know the details.  What chambers did the cylinder start with?  And give us an idea how much the conversion cost?

[The_Shadow]

Need pictures too!