How to work with threaded barrel parts so things line up?

[Maillemaker]

OK, probably stupid question time:

When you have threaded barrel things, like, say, the barrel on an Remington New Model Army Revolver (1858), that threads into the frame, how is it manufactured so that when you thread the barrel into the frame it stops at the right place?

Same thing when you make a breech plug for a barrel - how do you make it so that the tang lines up where you want it to stop on the barrel?

Are the threads cut so that they start and stop at special places to make this happen? Or do you just cut the threads randomly and then remove material from the plug face or barrel face until things bottom out in the correct location?

If you put things together the first time and things bottom out just past where you want, that would mean you'd have to remove one pitch's worth of threads of material to get back to the right starting point, right? That seems like a lot of manufacturing variability in overall length?

Can someone explain how this works?

Thanks,

Steve

[MR. GADGET]

When the barrel is blueprints it gives a known start point and is cut to be timed correctly when turned onto the reciever.
take M1 garand, m1 carbines and 1903
the barrels are made so they time in correct to the design.
it will turn in the set it to top and you are done.
True on some they may be different due to tolerance stacking but most can be set by just a little work on the shoulder if needed.

[Maillemaker]

Thanks for the info!

OK, so it comes down to the threads have to be cut correctly.

Now the $30K question: If I wanted to remove the breech from an Armisport M1842 barrel, and have a new breech machined to look like an H&P bolster as seen on M1840 H&P Conversions, how would I specify the threads to be like the M1842 so that the new breech would screw in and stop at the same location as the original 1842 breech?

I suppose I could give the M42 breech to the machinist and say, "Make the threads like this one", but ultimately I will need to know correct machinist-speak to have a drawing made so that they can be manufactured.

My intent is to have a custom breech machined from billet steel to end up with a reproduction H&P M1840 conversion barrel.

Next step is a custom reproduction M1840 lock plate but that is relatively easy.

Steve

[MR. GADGET]

Best way is to show them both and let them find away to clock it.

Not sure the threads would be the same or even cut the same for some of the old guns.
what they would do is make the breech and thread it they cut the shoulder back.

The repops use a different type then the old 42 or other guns if I remember.
it would be really hard to copy.
Your smith should be able to measure it and build something or a tool to set up threads to get a start point to cut the new threads.

Not sure on the barrel you want to make but maybe have your breech made threaded then use a barrel blank and install. Should not matter how it treads on just install. After that you could cut the flat sides or contour the barrel. Then trim and crown the barrel to correct length.

If you are doing the barrel and the work, why not build with a new barrel that would be better quality than a takeoff repop?

[Bruce Cobb 1723V]

If you make a tang, the very first thing you do is fit and machine a chunk of threaded metal to to the breech first so that it clocks maybe 10 degrees from lining up. Then you machine and finish the tang portion. If you make a bolster you turn the barrel breech to a diameter without threads. You machine the new bolster with a hole in it to slip over the turned barrel diameter. You then silver solder it together. Easy

[Eggman]

Better do what Bruce says Steve. He sits right next to John Holland on the Small Arms Committee.

[John Holland]

Actually, Bruce is giving you the benefit of having worked with Jerry Harmon and his breeching process.

[Maillemaker]

Where this is going is my intent here is to try and make a reproduction H&P conversion of an M1840. Since the M1840 is nearly identical to the M1842, my intent is to start with an Armisport 1842.

I am going to have a reproduction breech made to look externally like the H&P "small snail" bolster, as is correct the the H&P M1840 conversions. But internally it will look like an Armisport 1842 breech. The intent is to utilize the Armisport barrel and marry the new custom breech to it. By keeping the rest of the external dimensions of the breech to match the repro 1842 breech (except the bolster of course), the intent is for it to drop back into the 1842 stock with minimal work to the stock.

The intent is to re-use the Armisport barrel to save costs. This precludes a slip-fit and solder operation. It will be necessary to reverse-engineer the Armisport breech so that the new breech locks into place as the original breech did. My hope is that all Armisport 1842 breeches are interchangeable with any Armisport 1842 barrel. If they are all custom fitted, then the project may be over before it starts. Or, another possibility is to shop out the work to a reputable barrel maker like Hoyt or Whitacre to have the new breeches fitted. Of course this will add cost.

I am seeing that some M1840 conversions had the bayonet lug on the top of the barrel - I need to confirm the correct location of the lug. It may be that the Armisport 1842 barrel needs to be rotated 180 degrees from its current orientation to work. This will have the happy consequence of hiding the Armisport markings under the stock.

I am also going to have a reproduction M1840 lock plate made. This will be designed to utilize existing Armisport M1842 lock internals and hammer.

It may be possible to salvage the Armisport 1842 stock with judicious reshaping near the wrist - I am not sure at this point. Worst case, a Dunlap stock will be required.

I believe I can make the project come in under $2000 - if the Armisport 1842 works as a basis for the conversion and all that is required is a new lockplate and breech.

And to head off the inevitable, "You should just buy an original", you will never find an un-issued condition H&P 1840 conversion for $2000 (and many of the M1840s sent for conversion were never issued). Even pitted "shooter" H&P conversions now start at around $1500 ( http://www.gunbroker.com/item/665135539 ).

This is mostly a project of personal edification. If the current Armisport 1842 would re-pass N-SSA inspection, then it is possible I will produce something for SAC inspection and card issuance. If it turns out to be manufacturable, it may turn into a limited run product.

Steve

[MR. GADGET]

Have you talked to DP about to see if there is a thought about doing a repop.

They were looking at the H&P repops but based on a 1816 if I remember.

Who knows. I bet they would sell a bunch if they pulled it off.

[Maillemaker]

I had originally pestered both Pedersoli and Chiappa about doing an 1816 conversion. This was before I re-learned that some of the H&P federal contract conversions were made on M1840s, which I learned are nearly identical to the M1842. I now think going the M1840 conversion route is the most feasible to pull off.

As I understand it, Pedersoli's 1816 is not a faithful reproduction and it is doubtful if it would pass N-SSA approval today. Evidently the stock is based on their 1777 Charleville, as I am given to understand.

If a commercial company were to undertake it, I would think Chiappa could do it quite easily based on their existing 1842. No doubt I'll get the new breech and lockplate designed and they'll come out with it.

Steve