So. Yesterday I began the saga of trying to make an federal contract H&P Conversion of an M1840. The M1840 conversion is an enticing candidate because the M1840 is nearly identical to the M1842. I would have preferred to make an M1816 conversion, since they seem to have been more common, but no one makes a very accurate M1816 reproduction musket today. Pedersoli makes one, but the word is that they basically modified their 1777 Charleville to look sort of like an M1816, but it is not a very accurate reproduction of it. So it is unlikely that if it had to pass N-SSA approval muster today that it would.
But Chiappa / Armi Sport makes a very acceptable reproduction of the M1842, so my hope is to use it as a starting point for "retrograding" it to an M1840.
So, a little bit of history of the H&P conversions. This document is dated and is said to make some broad generalizations that have since been refined since this article was written, but this is a good summary of the H&P conversions:
http://americansocietyofarmscollecto...33_Altemus.pdf
Basically, at the start of the American Civil War, both sides were unprepared. There was an acute shortage of weapons. The weapons stored in the federal arsenals included many flintlock smoothbore arms, including M1816, M1822, and M1835/1840 muskets. H&P had a federal contract (and a state contract for the state of New Jersey) to convert these firearms to rifled percussion arms. The New Jersey arms can be easily identified by the clean-out screw on the bolster. All of them were rifled. The federal contract arms, which numbered just over 12,000, were intended to be rifled, and so were equipped with rear sights. But due to the pressing need for arms, they were sent out still as smoothbores. Hence the high desirability of such arms in N-SSA comptition - with our carefully-tuned target loads a rear sight is considered by many to be a valuable asset.
The way the H&P conversion worked was to cut off the breech end of the flintlock barrel, and then thread a newly-made percussion breech in its place. Some of the flintlocks had already been converted to percussion using the "cone in barrel" method, and these too were re-converted to the new bolster breech. So some of the arms had more of the breech end of the barrel cut off than others. But the effect is the same - the breech end of the barrel was cut off, and a new breech screwed into place.
The H&P breech contained a chamber that was smaller in diameter than the .69 bore of the barrel. This meant a special cleaning rod was required to adequately clean the chamber.
For my project, the idea is to keep the number of custom modifications required to a minimum.
To this end, for the breech, what I am going to do is create a 3D model using Computer Aided Design (CAD) software. This new breech will be dimensionally identical to the Armi Sport breech, internally and externally, with the exception of the bolster geometry. This will be shaped above the stock to look more like the H&P bolster, and will be shaped below the stock so that there is additional material required to fit into the notch on the M1840 lock plate. By maintaining the same internal geometry as the Armi Sport breech, the new breech will not have the deficiency of the original H&P breech with the reduced chamber diameter. This will make cleaning as easy as it is on the 1842. By maintaining the same external geometry as the Armi Sport breech, the entire barrel assembly should drop back into the Armi Sport stock without problems.
For the lock, my plan is to make a 3D model of an original M1840 lock plate, and then modify it as needed so that it directly accepts the Armi Sport 1842 lock internals. Most of the internals, except the mainspring, are very close to the original components already, so this should not be difficult. In fact, test fitting indicates that the bridle, tumbler, and sear all fit the original lock plate, right down to the screw threads.
I was able to obtain an original M1840 lock plate that had already been used in a cone-in-barrel conversion, complements of Lodgewood Manufacturing. While I wait for them to get a new batch of Armisport 1842s in, I decided to start working on the lock plate:
Right now I am modeling the original plate exactly. After I get it done, I will start modifying it to accept the Armi Sport 1842 internals. As I mentioned previously, I already did a check fit using my Armi Sport 1842 I already own, and most of the lock internals are drop-in replacements. The bridle and sear fit. The hammer hole will need to be enlarge slightly. The biggest change will be to reposition the holes for the mainspring as the Armi Sport spring is slightly different from the original.
Then I will 3D print for a fit check.
Sadly, it does not appear that there is enough wood in the Armi Sport 1842 stock to do the trick. There is enough wood for the mortise to work, but there is not enough wood to make the full "picture frame" on the escutcheon on the sides of the stock to fully frame the lock in wood.
I believe I am going to try and cut way a portion of the stock at the end of the lock opening, machining a flat chunk out of it with a router, and then splice in an "extension" of walnut to the back of the mortise hole, which can then be re-shaped. The alternative is a Dunlap stock, but this will be much more expensive and probably require more work.
I will post updates as they happen.
Steve
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