1871 Vetterli Conversion: converting an old Swiss Vetterli 1871.41 Swiss to centerfire. here's a modern way to conduct the conversion with the help of a 3D printer.
In the due course of events, I inherited a Swiss Vetterli 1871. From my earliest memories seeing it leaning against a wall in my grandfather's attic the rifle had fascinated me. A good bit of family apocrypha surrounded the rifle, not the least of which being that my grandfather's friend, from whom he had inherited the rifle, had begun boring out the barrel in preparation to convert it to an available rimfire caliber. This I took at face value for years.
The omniscience of the Internet ultimately gave the old rifle new life. Upon doing a little research I discovered there is a small community of shooters who have converted by a variety of methods the various models of the .41 Swiss Vetterli to shoot centerfire ammunition and that reloading dies were available. This inspired me to consider how to convert my rifle, if it was sound.
The first task was to take down the rifle and give it a thorough cleaning. The dust of well over 60 years had worked its way into the inner workings and the oil inside had turned to varnish. On scrubbing out the barrel, I was delighted to find that it looked nearly like new, with sharp rifling and no discernible wear or corrosion or, contrary to rumor, tool marks.
The next task was to slug the chamber and the bore. A couple of quick sessions with Cerrosafe confirmed the rifle was chambered for .41 Swiss, the rifling remained sharp, and the grooves measured 0.429" as per specification. This resulted in an order to Buffalo Arms (BuffaloArms. com, 208/263-6953) for 25 rounds of .41 Swiss brass (converted from 8mm Lebel cases) and to Midway for reloading dies, a bullet sizing die, and 330 grain .430 RN bullets.
My goal in converting my Vetterli was to minimize irreversible changes to the bolt, keeping it as nearly original as possible, and permitting return to its original condition if desired in the future. The only permanent change that my method entails is a hole bored in the bolt face to accommodate the center fire pin. Otherwise, my approach simply replaces the original wishbone-shaped firing pin with a modified replica with shorter arms that don't extend beyond the bolt face and includes a centerfire firing pin.
The Vetterli Bolt
The first task in the bolt conversion is to remove the bolt from the receiver. This is a little more involved than with a modern bolt action. It requires drifting a split wedge retainer in the top of the rear of the receiver out to the left with a screwdriver--the wedge is designed to remain in the receiver when it is clear of the bolt--and removing the loading tray out the bottom of the receiver by backing out the retaining bolt from the left side of the receiver. When this bolt is removed, the entire loading mechanism--the cam and the tray--will drop out the bottom of the receiver. With the retainer wedge pulled out to the left, the bolt will slide effortlessly out the back of the receiver.
The bolt comprises eight pieces: Bolt body, extractor, handle, rear shroud, back retaining nut, spring, striker rod, firing pin. There is no safety. Further, the bolt body does not rotate. Rather, the bolt handle rotates and locks the bolt in place at the rear of the receiver.
To disassemble the bolt, take a firm grasp of the body around the shroud at the rear and unscrew the retaining nut from the back of the bolt. The nut compresses the firing spring, so care needs to be taken when backing it out, lest you inadvertently distribute parts all over the shop. Once the nut is free, the shroud, striker, and bolt handle will all come off the rear of the bolt body.
The firing pin rides in a slot machined through the bolt body at the forward end. It is a wishbone-shaped piece of metal, with the base of the wishbone fitting over the end of the striker rod and the wide ends of the wishbone riding in slots machined at 3 and 9 o'clock in the sides of the bolt head. The extractor is on the top. When the trigger is pulled, the striker rod is released to be propelled forward by the spring, pushing the wishbone-shaped firing pin forward. The ends of the wide (forward) part of the wishbone then strike the rim of the cartridge 180[degrees] apart. With the striker rod removed, the firing pin can be taken out through the side of the bolt body.
I decided to first bore a hole in the bolt face. I chose to use a (notionally) 0.061" de-capping pin for a firing pin, so I bored the hole with a number 50 drill. Rather than trying to set up the bolt body in the drill press, I chucked it up in my lathe and put a chuck in the tail stock to bore the hole. The bolt face is 0.280" thick, but it's not especially hard, and it's perfectly flat except for a numeral "8" stamped in the center.
My first attempt at recreating the original firing pin on my milling machine involved using a piece of thin bar stock and milling a replica of the rimfire firing pin, shortening the arms of the wishbone such that in its forward most position they would not extend past the bolt face. This I accomplished without incident, including boring the hole for the striker rod. However, when drilling the hole in the center of the crotch of the wishbone to accommodate the firing pin, my drill broke in the hole, ending that effort.
Following some color commentary that had a sad effect on the paint on my milling machine, I stopped to reconsider. The wishbone, in the centerfire configuration, is simply a mechanism to hold and guide the firing pin. Of itself, it doesn't really require a lot of strength and what strength it does require is in compression. So a piece of plastic should do. With this in mind, I mailed my failed sample to my brother, an engineering professor in the SUNY (State University of New York) school system and who, more importantly, has a 3D printer and Computer-Aided Design (CAD) expertise and software.
A couple of weeks later he had scanned the sample into his CAD software, cleaned it up, added a pilot hole for the firing pin, and printed five bright yellow ABS plastic wishbones and sent them back to me. All that was required was to finish fit the wishbone to the bolt--the hole for the striker rod in the base of the wishbone needed to be relieved a bit and the hole for the firing pin needed to be opened a bit with a number 53 drill.
With this accomplished, all that remained was to reassemble the bolt and test the function. The wishbone with the firing pin inserted will not fit into the slot in the bolt body. I put a very small dollop of quick-curing epoxy in the hole for the firing pin, then inserted the wishbone into the bolt body and slid the striker rod in to hold the wishbone firmly against the inside of the bolt face. I then inserted the firing pin through the hole in the bolt face and into the wishbone and let the epoxy set. If I need to remove the assembly, I can grab the firing pin with a pair of pliers and pull it out, but in normal operation the epoxy should keep it in place even if dry fired.
I confirmed that the wishbone had free travel in the bolt face, then reassembled the bolt. This is simply a reversal of the disassembly. If you try to do anything out of order, the bolt will let you know. The only tricky part is getting the retaining nut started against the spring, but it's just a little fussy, not difficult.
I loaded primers into five cases and loaded one into the rifle. With appropriate eye and ear protection, and the muzzle pointed into a box of rags, I pulled the trigger and was rewarded with a sharp snap and the pleasant smell (as far as I was concerned--the distaff side of the family had a different take) of a fired primer. I also had a primer with a hole all the way through it. So a little dressing with a fine grinder on a Dremel tool and a couple of additional test shots got the firing pin length adjusted. The final length was 0.568".
Firing The .41 Swiss
There is not much load data for the .41 Swiss. I was leery of using smokeless powder, although various user forum entries suggested using Unique, 5744, 4198, Blue Dot, and other smokeless powders in small quantities. This seemed to me to be inviting problems. The .41 Swiss case, while not large, is still big enough to make a small charge of powder a challenge to ignite. Plus, even though the original ammunition transitioned to early smokeless powder, it was designed for black powder and the smokeless was most likely pretty low pressure, low density stuff.
With this in mind, I decided to test fire the rifle using FFg. I found that the maximum uncompressed volume of FFg that the cartridge would take was about 38 grains, so I loaded five rounds with 35 grains of FFg behind a 330 grain round nose bullet sized to 0.429" with an overall length of 2.2". This seems to be critical to proper feeding if you want to use the side-loaded tubular magazine. It also seems to be a pretty close replica of the original.
My brother the professor was in town with his family for Thanksgiving and we test fired the rifle on a steel plate on the 200 meter range at the Fairfax Rod and Gun Club on Friday after Thanksgiving. For the first round out of the muzzle in the better part of a century, I braced the rifle carefully with the muzzle pointed at the berm and pulled the trigger from a discrete distance. The rifle stayed in one piece, the bullet hit the berm and neither the bolt nor the empty showed any signs of distress, We proceeded to see what we could hit. With nephew Matt spotting, I aimed about a foot above the top of the steel plate target at 200 meters, figuring that the trajectory would be like a mortar. When I squeezed off the round, there was a light recoil, a large volume of delicious black powder smoke, and Matt announced that the dirt kicked up directly above the target.
For the second round I aimed at the middle of the plate and squeezed again. There was a bang, a pregnant pause, then a clang as 330 grains of Midway's best lead hitting the target. The subsequent two shots had the same result.
After spending some considerable time cleaning the rifle, I decided to revise my thinking on smokeless powder and looked for one that was bulky enough to mostly fill up the case without creating dangerous chamber pressures. I found the answer in IMR's Trail Boss. Another shooter had tried 13 grains of Trail Boss behind a 310 grain lead bullet with good results. I compared that load to one listed at AmmoGuide (AmmoGuide.com) for the similar Italian Vetterli 10.4x47R and to the .45-70 Trail Boss loads, finding that 13 grains seemed reasonable. Further research on AmmoGuide revealed a similar load. Upon testing, I found that the maximum uncompressed load of Trail Boss was about 13.5 grains, so I loaded five rounds with 12 grains of Trail Boss behind the same 330 grain lead RN bullet.
I tested this on a paper target at 40 yards. The rifle shot about nine-inches high with the sight bottomed, so the first round was off the paper. The second round, aimed about halfway down the target was about 4" high and the subsequent rounds aimed at the bottom edge of the target were dead center, with about an inch of displacement left and right total. Subsequent experimentation confirms that the rifle is zeroed at 200 meters and even with the ancient sights offers sub-minute-of-pie-plate accuracy.
While not especially powerful, the .41 Swiss Vetterli is pleasant to shoot with these loads and clearly quite accurate with 140 year old military iron sights. Other shooters report using 240 grain .44 Magnum bullets with essentially the same powder loads with similar success.
This rifle is not uncommon and not particularly expensive. The conversion process is straightforward, reloading dies are available from RCBS, and brass is available or can be converted from .348 Winchester or 8mm Lebel with a few evening's effort. As a fun project and an even more fun shooter, the .41 Swiss Vetterli has a lot to recommend it.
While not the simplest Vetterli conversion procedure, I am convinced this is a fairly simple, easily executed, and technically sound approach. Marrying the 21st century technology of CAD and 3D printing to a 19th century firearm results in a minimally-disruptive modification that uses all of the original parts in their designed roles and configuration. The only exception is the firing pin replaced with a shorter replica and a small hole in the bolt face to accommodate the new center fire firing pin.
The 3D printed part is inexpensive and can be produced in quantity, allowing for spares and mistakes. Further, 3D printers of adequate precision can be had for under $1000 and there are several good, free CAD programs available, including one from Google called SketchUp (SketchUp.com).
In applications like this conversion where the properties of steel aren't necessarily required for the function, 3D printing could have a regular place in the resurrection of old firearms and even in the repair and modification of more modern arms. All without the hysteria generated by the printing of an entire firearm.
by Kevin Baxter
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|Date:||Jul 17, 2017|
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